L. L. Khalfin.

Middle Devonian Brachiopods from the Village of Lebedyanskoye, Anzhero-Sudzhensk District

PREFACE

The Devonian deposits exposed along the Kitat and Alchedat rivers near the village of Lebedyanskoye constitute, for the northern margin of the Kuzbass, a quite exceptional locality of Devonian fauna in terms of its abundance and excellent preservation. Alongside a whole series of bedrock outcrops in which the fauna can be collected in situ, the talus slopes and river gravels contain an enormous quantity of organic remains, often of ideal preservation, obtained as a result of their natural preparation.

A detailed study of this rich paleontological material is a rewarding task and should be of substantial importance for refining the stratigraphic correlations within the Devonian system of Western Siberia in general and of the Kuzbass in particular. The study of the well-preserved Lebedyanskoye fauna will considerably facilitate the study of coeval deposits in other districts, where the fauna is often much more poorly preserved. This latter circumstance, given the weak development of Siberian paleontology, often greatly complicates the solution of stratigraphic problems, and in such cases knowledge of the fauna from its richest localities should have significance extending beyond the geology of the given area. For the upper parts of the Siberian Middle Devonian, such significance belongs to the Lebedyanskoye fauna. Nor is this diminished by the fact that, owing to the complex tectonics, the field observations that have been made do not permit the construction of a continuous stratigraphic section linking the numerous but isolated exposures of Devonian rocks near Lebedyanskoye.

The immediate practical significance of studying the fauna of the Devonian deposits of the village of Lebedyanskoye is determined by the circumstance (as will be set out in more detail in the conclusion) that these deposits are the stratigraphic equivalent of part of the sapropelite productive sequence of the neighboring Barzas district.

Lithologically, the Devonian deposits of the village of Lebedyanskoye consist of an alternation of thin beds of shales, marls, and limestones. East of the village of Lebedyanskoye there is a mass of coral limestone. The tectonics of these rocks reflects a major disturbance at the boundary between them and the productive sequence of the Anzhero-Sudzhensk district: the rocks under consideration are gathered into small folds of various orientations and are cut by numerous small disjunctive disturbances. The general dip of these rocks is westward. For a characterization of the geology of the surroundings of the village of Lebedyanskoye, see the article by K. V. Radugin (54) on the tentaculites of the Lebedyanskoye Devonian.

The facies character of the Lebedyanskoye Devonian rocks is quite clearly determined both by their lithological composition and by the fauna contained in them. These are deposits of a shallow but open marine basin with an unstable regime and frequently changing sedimentation conditions.

The fauna of the Lebedyanskoye Devonian is represented by all types of invertebrates. However, decisive quantitative predominance within it belongs to brachiopods and tentaculites. The brachiopods treated by the author of this article, and

below, a detailed description of them is given. The corals were worked up by K. V. Radugin, whose work is in press. The bryozoans in the Lebedyanskoye Devonian are very numerous and diverse; unfortunately, this group of fossils of the Lebedyanskoye Devonian still only awaits study. Mollusks are very few in number. Cephalopods are represented by rather rarely encountered large representatives of the genus Gomphoceras. Gastropods are more numerous, but monotonous, being represented almost exclusively by small Capulidae. Pelecypods are still rarer. Trilobites, belonging to small Phacopidae and Bronteidae, are also few in number.

Plan of the village of Lebedyanskoye

Scale.

The collections of brachiopods of the Lebedyanskoye Middle Devonian described in this article were assembled at different times by various geologists. In the Cabinet of Historical Geology of the Tomsk Industrial Institute named after S. M. Kirov are kept collections of the Lebedyanskoye fauna made by M. E. Yanishevsky, M. A. Usov (1919), and M. K. Korovin (1917). The collections of M. E. Yanishevsky are not numerous, but contain a number of interesting and rare forms absent from other collections (for example, Trigeria lata n. sp., Meristella yanischeveskii n. sp.). In the collection gathered by M. K. Korovin, of special interest is a group of anathyrids found in the northernmost outcrops of the Lebedyanskoye Devonian along the Kitat River. The collections of M. A. Usov are distinguished by great completeness and systematic character. Unfortunately, it is not possible at present to establish the exact locality for all specimens of these collections, which were assembled comparatively long ago.

In the summer of 1931, a substantial collection was gathered by the author during his three-day stay in the village of Lebedyanskoye.

The material represented by these four collections is very extensive, but it hardly exhausts all the diversity of the Lebedyanskoye fauna. This is indicated by the circumstance that in each of the collections there are forms,

absent in the others. In this respect, the systematic collections of the Lebedyanskoye fauna made in the summer of 1933 by K. V. Radugin should be of great interest. The processing of the material from these collections will not present special difficulties after the processing of the above-listed collections, and will make it possible to clarify the distribution of individual forms in the Lebedyanskoye Devonian.

The collections whose fauna is described in this article came into the author’s possession in a partially processed state. A number of specimens were furnished with labels bearing species names according to the determinations of M. K. Korovin. The latter established two new species—Spirifer (Delthyris) altschedatiensis and Spirifer (Hysterolites) mesolobus, descriptions of which are given below. For the following forms, M. K. Korovin’s species determinations remained unchanged: Leptaena rhomboidalis Wilk., Schellwienella umbraculum Schl., Schizophoria striatula Schl., Uncinulus (?) subsignatus Reed, Spirifer cabedanus V. et A., Spirifer cf. argentarius Meek, Spirifer undiferus Roem., Spirifer cheehiel Kon., Cyrtina heteroclita Defr., Atrypa reticularis Linn.

In addition, M. K. Korovin studied the details of the internal skeleton of representatives of the group Spirifer cheehiel; A. V. Aksarin also took part in this work. All observations on this question were kindly communicated to the author by M. K. Korovin.

V. K. Khalfina and M. M. Vrachinskaya took part in the work on determining the Lebedyanskoye brachiopods.

The author expresses deep gratitude to M. K. Korovin, to whom belong the general direction of the author’s work and the editing of the manuscript.

1934, February.
Tomsk.

DESCRIPTION OF THE FAUNA

Chonetes coronata Conr.

1. Chonetes coronata: Hall. Pal. N. Y., vol. IV, p. 133, pl. XXI, figs. 9—12.
2. Chonetes coronata: Schuchert, Bull. U. S. Geol. Surv., p. 173.
   ? 1905. Chonetes coronata: Thomas. Zeitschr. deutsch. geol. Ges. LVII, S. 259, Taf. XIV, Fig. 39, 40.
3. Chonetes coronatus: Prosser and Kindle. Maryl. Geol. Surv., Middle and Upper Devonian, p. 148, pl. XI, figs. 18—21.
4. Chonetes coronatus: Branson and Williams. Dev. of Missouri, p. 138, pl. XXXII figs. 1—3.
5. Chonetes coronata: Nalivkin. Brach. mid. and upper Dev. Turk., p. 29, pl. II, fig. 23.

One specimen in our collection is a piece of yellowish-gray marly sandstone with numerous impressions of isolated valves of Chonetes coronata. Specimens of this species in the Lebedyansky Devonian reach 18 mm in width and possess a clearly expressed sinus, showing complete similarity with the Maryland Middle Devonian representatives of Chonetes coronata.

This species is widely distributed in the Hamilton deposits of North America. Nalivkin cites it from the Eifelian stage of Turkestan. A close, but scarcely identical form to this species was described under the name Chonetes coronata by Thomas from deposits of Argentina, which this author regards as Lower Devonian, but which possibly are also older (9, 16).

Chonetes cf. subcancellata Reed.

One dorsal valve, visible from the inner side, has the following dimensions: length—6 mm, width—10 mm. The length of the hinge margin is somewhat less than the greatest width of the shell. The number of radial ribs is not less than 40. The spaces between the ribs on the inner surface of the valve are set with small tubercles. The number of the latter in one row from the beak to the margin of the valve reaches 15.

The specimen shows complete similarity with dorsal valves of Chonetes subcancellata Reed from the Middle Devonian Wetwin Shales of Burma (55, 160). Only the insufficiency of the material prevents complete identification of this specimen with Reed’s species. The close Chonetes minuta Goldf., var. tuberculata mihi from the Upper Devonian of the Kuzbass (34, 11) differs in somewhat smaller dimensions, a smaller number of ribs, and the presence of concentric corrugation. The specimen comes from the Alchedat River.

Productella subaculeata Murch.

1. Productella subaculeata: Khalfin. Brachiopods of Cherepanovo Ford, p. 7, pl. I, figs. 1—2.

Specimens of this species are rather numerous in the Lebedyansky fauna. They do not differ in any way from representatives of Productella subaculeata from the Lower Frasnian deposits of the Kuzbass (see synonymy).

Productella spinulicosta Hall.

1. Productella spinulicosta: Petz. Materials on the knowledge of the fauna of the Devonian deposits of the outskirts of the Kuzbass, p. 58.
2. Productella spinulicosta: Khalfin. Brachiopods of the Cherep. ford, p. 8, pl. I, fig. 7.

Productella spinulicosta from the Devonian deposits of the Kuzbass has been described in the works cited in the synonymy. This species is common in the Lower Frasnian deposits of Siberia; Petz cites Productella spinulicosta from the stringocephalid deposits of the western margin of the Kuzbass.

In the Lebedyanskoye Devonian, Productella spinulicosta belongs to rather rare forms. It was found on the Alchedat River, above the mouth of the Kamenushka stream.

Stropheodonta asella Vern.

(Pl. I, figs. 1–5).

1. Leptaena asella: Verneuil. Paléont. de la Russie, p. 224, pl. XIV, fig. 3.
2. Stropheodonta perplana, var. nervosa: Hall. Pal. N. Y., vol. IV, p. 113, pl. XIX.
3. Strophomena asella: Venjukov. Fauna of the Devonian system etc., p. 60, pl. II, fig. 14.
4. Stropheodonta perplana nervosa: Schuchert. Synopsis of Am. Foss. Brach., p. 426.
5. Stropheodonta asella: Petz. Materials on the knowledge of the fauna etc., p. 68, pl. V, fig. 17.
6. Stropheodonta asella: Nalivkin. Semiluki and Voronezh beds, p. 70.
7. Stropheodonta asella: Khalfin. Upper Devonian brachiopods of the Cherep. ford, p. 9, pl. I, figs. 9, 10.
8. Stropheodonta asella: Khalfin. Lower Frasnian brachiopods of the outskirts of the Kuzbass etc., p. 6.

Specimens of this species are fairly common in the fauna of the village of Lebedyanskoye and consist of shells of medium and rather large size, of regular rounded outline, with a hinge margin drawn out into pointed extensions, which are very rarely preserved. The ventral valve is weakly convex, the dorsal one weakly concave or flat. The dimensions of the largest specimens are 30–40 mm in width (not counting the pointed auricles) and 25–30 mm in length; the auricles reach a length of half a centimeter each. The usual dimensions are somewhat smaller. There are specimens that scarcely reach a centimeter in width.

The area of the ventral valve is not high (1.5–2 mm in height); the number of vertical denticles on it is about sixty. These denticles are most densely arranged near the delthyrium, and here they extend across the entire area; nearer the cardinal angles they become shorter, occupying only the lower part of the area, and finally disappear completely; the ends of the area are smooth. The delthyrium is narrow, closed by a pseudo-delthidial plate. The area of the dorsal valve is very low, likewise provided with denticles.

In the ventral valve there is a thin and low median septum, reaching one-third of the shell length. The impressions of the diductor muscles are fan-shaped, anteriorly almost not outlined, merging with the rest of the surface of the valve; laterally they are bounded by two sharp, diverging ridges, forming angles of 52°–56° with the hinge margin. In most cases, of the details of the internal structure only the median septum and the two ridges bounding the diductor impressions are preserved. The teeth and impressions of the adductors have not been preserved in our specimens.

The elements of the internal structure of the dorsal valve in S. asella, in general, are very weakly developed. In our specimens one can distinguish very short (about 2 mm long) diverging ridges (analogous to those in the ventral valve), bounding the place of attachment of the adductors. Between these ridges lies an even shorter and weaker median septum. In general, the internal structure of the dorsal valve resembles that of the ventral valve, but its elements appear in a diminished—

in a weakened form. The interarea in our specimens has not been preserved.

The sculpture of the outer surface of the valves consists of thin rounded costellae, some beginning at the beak, others appearing later at various distances from the beak; near the margins of the valve they all have approximately the same thickness; their number (along the margin of the valve) is 50–60. A certain irregularity of the costellae is very characteristic: along the course from the beak to the margin of the valve almost every costella several times either thickens or becomes thinner, not infrequently bends in a wave-like manner, at times even breaks off and then is restored again. In general, the costellae situated near the plane of symmetry are rectilinear, whereas on the lateral parts of the valves, especially near the cardinal angles, they become curvilinear, bending toward the hinge margin. The spaces between the costellae are of unequal width and flat. Within them are situated thin, thread-like, wavy striae (like the costellae). The number of these striae between two neighboring costellae varies from one to four, usually two to three. Through the thickening (often sudden) of one of these striae, a costella of the second or third order is formed; therefore, near the margin of the shell the number of striae between neighboring costellae is usually smaller (often one stria) than at some distance from the margin. On well-preserved specimens the finest concentric striation is clearly visible. False porosity is well expressed.

Specimens of S. asella from the Lebedyanskaya fauna are wholly identical with specimens of this species from the Frasnian deposits of Kuzbass, which specimens, as has already been noted in the literature (32, 9), differ from the Semiluki specimens of the Voronezh Devonian by a flatter shell: the ventral valve in the Siberian specimens is very weakly convex, and the dorsal valve is often flat.

The Stropheodonta perplana, var. nervosa occurring in the Portage and Chemung group of North America differs, as was already pointed out by Petz (51, 69), from S. asella only in its flat dorsal valve. The Lebedyansk material, as noted above, makes it possible to establish that, alongside convex-concave specimens, the species S. asella also contains plano-convex ones, and that all transitions exist between the former and the latter. Only the impossibility of making a direct comparison compels us to place a question mark by S. perplana nervosa in our synonymy of S. asella.

Very close to S. asella in external characters is the form described by Reed (55, 66) from the calceola beds of Burma under the name Stropheodonta interstrialis Phill., n. var. birmanica. The essential differences lie in the internal structure: the latter form belongs to the genus Douvillina Oehl.

The presence of S. asella in the Lebedyanskaya fauna shows that the distribution of this species in the Devonian of Kuzbass is not limited to the Frasnian stage, but also includes the upper part of the Middle Devonian.

Numerous specimens of S. asella have been found in outcrops along the Alchedat River.

Stropheodonta reticularis n. sp.

(Table 1, fig. 6).

This elegant form, possessing very characteristic features in its sculpture, is represented in our collection by only four specimens. It is not possible to identify it with any of the species described in the literature available to us.

The shell is concavo-convex, elongated in the transverse direction. The greatest width coincides with the hinge margin. There are well-developed,

triangular in outline. The ventral valve is moderately and regularly convex, the dorsal valve—considerably concave; as a result, the valves are closely appressed, and the cavity between them is extremely slight.

The area of the ventral valve is very low (1–1.5 mm high), denticulate; the area of the dorsal valve is still more weakly developed, almost linear, but likewise supplied with small denticles, as is the area of the ventral valve.

The sculpture of the outer surface of the valves is very characteristic, consisting of radial and concentric elements. Very fine rounded costellae are present in considerable number on both valves; on the lateral parts of the valves they bend noticeably toward the cardinal angles. They rapidly increase in number by intercalation: already at a slight distance from the beak their number reaches 36 on the larger specimen and 30 on the specimen of smaller size. Only half of this number reaches the very beak. In places intercalation of costellae of a third order is observed, but far from in all intervals. Moreover, these costellae of the third order are very fine and often difficult to distinguish from the striae occupying the intervals between the costellae. The costellae themselves are not regularly rectilinear: along the extent from the beak to the margin of the valve each costella bends smoothly in a wave-like manner several times. The intervals between the costellae are broad and flat; they are occupied by very fine striae, three or four and more (up to eight) in each interval.

The entire surface of the valves is covered with concentric wrinkles, to some extent resembling the wrinkles covering the umbonal part of the valves of Leptaena rhomboidalis Wilck. In our species they are smaller and more numerous—20–25 on each valve. In the umbonal and beak region these wrinkles are very small; as they approach the margins of the valve they become larger, but even near the margins of the shell their width does not exceed 1.5 mm. The most important feature of these wrinkles is that they are expressed only in the intervals between the costellae: the latter cut through the wrinkles, dissecting them into short segments, which have the character of certain swellings, tubercles, situated in the intervals between the costellae. Each wrinkle is formed by a chain of these swellings arranged in a concentric row. In addition to the concentric wrinkles, there is also the finest concentric striation, which is rather poorly preserved (visible only in places). A false porosity is observed, as in representatives of the group Stropheodonta interstrialis Phill.

The internal structure cannot be observed on our specimens.

Of all known species of the genus Stropheodonta Hall, our species is sharply distinguished by the presence of the concentric wrinkles characterized above. The general appearance of the outer surface of the valves of S. reticularis somewhat recalls that of the Silurian Rafinesquina corrugatella Dav. (12, p. 301, pl. XL, figs. 8–14); but this resemblance is purely external: the concentric folds in Davidson’s species are formed by entirely different elements. The presence of radial costellae and of radial and concentric striae brings our species close to some species of the group S. interstrialis. Stropheodonta reticularis was found along the Alchedat River, by the cemetery.

Douvillina sp.

(Table 1, fig. 10).

To this genus there belongs in our collection only one fragment of a ventral valve, visible from the inner side. The impressions of diductor muscles, of a character typical for the genus Douvillina, are excellently preserved:

in the form of a deep cup with margins rather highly raised above the rest of the surface of the valve. In the middle of the impressions there passes a low septum, most massive in its anterior part. A moderately high, denticulate area is visible. The inner surface of the valve is finely tuberculate, with faintly indicated thin radial riblets.

Dimensions: width 20 mm, length ~18 mm. The greatest width corresponds to the hinge line. The cardinal angles are right angles. The convexity of the valve is considerable.

The Douvillina dutertrei Mitch., common in the Lower Frasnian deposits of Kuzbass (33, 5), differs from our specimen in the lesser convexity of the valve and in the somewhat different character of the diductor impressions: in D. dutertrei the latter are more extended in width and less developed in length than in the specimen described. The closest, and possibly identical, form is Douvillina birmanica Reed (55, p. 66, pl. XI, figs. 2, 5, 6); identification is impossible because of the insufficiency and defectiveness of our material.

Leptaena rhomboidalis Wilck.

(Table I, figs. 7–9).

This species is very widely distributed in the Lebedyanskoye Devonian. Its representatives show considerable variability in the number and character of the concentric wrinkles and in the degree of convexity of the ventral valve. The dimensions of the specimens vary within very wide limits: width—from 40 to 13; length—from 33 to 9.

In some specimens the concentric wrinkles are numerous (up to 15 on each valve) and regular. In others they are coarse, irregular, and few in number (7–8). The difference in the appearance of these specimens is very considerable, and, following the example of Öpik (47), they should be regarded as separate species.

The wrinkled part of the ventral valve in some specimens is completely flat, in others considerably convex. Two very large, strongly inflated ventral valves approach the Lower Devonian Leptaena ventricosa Hall. A specimen (Table I, fig. 9), which is an internal mold of a ventral valve with a strongly developed muscular platform, is also very close to this same species.

Specimens with a sinus-like bend of the frontal margin, characteristic of Leptaena bouei Barr., are absent from our collection.

In the Lebedyanskoye Devonian L. rhomboidalis is apparently ubiquitous, but specimens of this species are especially numerous in outcrops along the Alchedat River near the cemetery (see the plan of the village of Lebedyanskoye on p. 3).

Schellwienella umbraculum Schloth.

(Table II, figs. 11–14; Table III, figs. 22–23).

1. Streptorhynchus umbraculum (pars): Davidson. Brit. Foss. Brach. p. 76, pl. XVI, f. 6, pl. XVIII, figs. 1, 5.

2. Streptorhynchus umbraculum: Kayser. Brachiopod. d. Eifel, s. 615.

3. Orthotetes umbraculum: Whidborne. Dev. Fauna of the South of England, vol. II, pt. I, p. 146.

4. Orthis umbraculum: Oehlert. Bull. Soc. Géol. Fr., sér. 3, vol. XXIV, p.p. 856–867, pl. XXVII, fig. 9–11.

5. Streptorhynchus umbraculum: Gürich. Palaeoz. in Poln. Mittelgebirg., s. 229.

6. Orthis umbraculum (pars): Sobolev. Devonian Deposits of the Grzegorzewice, etc., p. 59, tabl. VII, figs. 16, 17.

7. Orthotetes umbraculum (pars): Sobolev. Middle Devonian of the Kielce-Sandomierz Ridge, p. 452.

8. Orthotetes umbraculum: Reed. Dev. Faunas of the North-Shan States, p. 75, pl. XIII, figs. 2–14.

9. Orthotetes umbraculum: Quiring. Strophonien. d. Mitteldevöns d. Eifel etc., s. 123.

This highly popular species still has no strictly defined and generally accepted limits, either systematically or stratigraphically. Some authors unite under this name several closely related but quite distinct forms, thereby giving Schlotheim’s species a collective meaning. For example, the Lower Devonian Orthotetes (?) hipponyx Schnur is often referred to this species, although rather substantial differences between these two species have been established by special studies. As an illustration of such a point of view, one may cite the conclusion of Hetmann (25, 331), who, although he recognizes the existence of differences between the Lower and Middle Devonian forms, nevertheless considers it possible to unite them under the common name Orthotetes (Schellwienella) umbraculum.

There can hardly be any substantial evidence in favor of such a union of forms having different stratigraphic positions, when there are at least slight but constant differences between them. As for this particular case, the extensive Siberian material at our disposal makes it possible, by direct comparison, to verify the existence of sufficiently clear differences between the Middle Devonian Schellwienella umbraculum and the externally similar forms from the Lower and Upper Devonian of Siberia.

The Lebedyanskoye specimens of S. umbraculum are entirely identical with the European and Asian representatives of this species described in the works cited in the synonymy; the most accurate figures of S. umbraculum are given in the works of Oehlert, Sobolev, and Reed. Unfortunately, many authors do not give descriptions of specimens of this species, considering it universally known, which, in view of the uncertainty in its scope noted above, makes it impossible to include a number of works in its synonymy. Below is given a detailed description of the Lebedyanskoye specimens of Schellwienella umbraculum.

The shells are of considerable and large size; regular, symmetrical; convex-concave to convex-plane. The width is always greater than the length. The greatest width of the shell coincides with the hinge margin. The cardinal angles are right, more rarely somewhat drawn out, acute, still more rarely slightly rounded; but even in the latter case the greatest width of the shell lies close to the hinge margin itself. The absolute dimensions vary within the following limits:

width	34 mm—75 mm
length	25 mm—55 mm

Large specimens predominate; only one specimen in our collection is 20 mm wide and 15 mm long. In our material there are entirely absent biconvex, asymmetrical, and small specimens.

The ventral valve is slightly concave, more rarely flat; in the umbonal part it is sometimes slightly convex. The area is straight, rather high, bent backward; the ratio of the height of the area to the length of its base fluctuates around 0.2. No striation can be observed on the area, which may perhaps be explained by the incomplete preservation of the material. The delthyrium is broad. In the ventral valve there are well-developed but short dental plates, rapidly diverging; the angle between the hinge margin and the direction of the dental plate is 40°. The dental plates continue into ridges surrounding large heart-shaped impressions of the diductor muscles. Both ridges, after curving around the impressions of the diductors from the lateral and anterior margins, meet on the median line of the valve and merge into a single ridge, which is directed toward the hinge margin but, before reaching the latter, again divides into two branches surrounding small, oval impressions of the adductor muscu-

The diductor impressions, as already noted, have a heart-shaped form; in some specimens they extend over more than half the length of the shell; their surface is covered with radial striation.

The dorsal valve is regularly convex, flat on the ears; in large specimens the convexity is greater than in specimens of medium size. In some individuals a longitudinal depression (sinus) is noticeable; such specimens are similar to variety 1 according to Sobolev (61, 59). This depression is sometimes clearly expressed, sometimes barely noticeable, more often entirely absent, and it never attains strong development. The area of the dorsal valve is very low and forms an obtuse angle with the area of the ventral valve. The cardinal process is short, massive, bilobed; each of its branches in turn has a small furrow dividing it in two. The impressions

Fig. 2. Schellwienella umbraculum: a—ventral valve, b—dorsal valve.

of the adductor muscles are larger, not sharply but noticeably delimited from the rest of the surface of the valve; their form is circular, and the surface is covered with radial striation. Along the plane of symmetry they are separated by a barely perceptible ridge.

The sculpture of the outer surface of the valves is well known: rectilinear riblets of several orders, increasing in number by repeated intercalation (intercalation, Einschiebung) at various distances from the beak. There is no dichotomous branching of the ribs; only occasionally, as a result of asymmetrical insertion of a new riblet relative to the two adjacent ones, does a certain external resemblance to dichotomy arise. There are several (not many) sharp growth marks, lamellar in character. Transverse notches on the riblets, their denticulation (crenulation), are clearly expressed in specimens that have fully preserved the outer layer of the shell.

Our specimens show complete similarity to representatives of this species from the Middle Devonian of India, excellent illustrations of which are given in the above-cited monograph by Reed. The European Middle Devonian specimens of S. umbraculum are just as close. As for the Lower and Upper Devonian forms described under this name, they are all substantially different: see, for example, the figures given by Kayser for the Lower Devonian (28, Taf. XXXIV, Fig. 1) and Upper Devonian (29, Taf. I, Fig. 11–12) forms of Germany. The differences between the Lower Devonian Schellwienella (?) hipponyx Schnur and S. umbraculum were clarified in full detail by Oehlert (45, 856–867) and supplemented by Drevermann (14, 116) and Assmann (2, 167).

At present, without revision of the corresponding materials, nothing definite can be said about the distribution of S. umbraculum within the USSR.

difficult. There is no doubt only that by no means all the forms previously described under this name in fact belong to S. umbraculum. Thus, for example, specimens from the Orel–Voronezh Devonian described by Venyukov (74, 53) under the name Streptorhynchus umbraculum, according to the latest data (42), belong to the species Streptorhynchus devonicus. Orb Chernyshov (68, 60) indicates the presence of forms, also named by him Streptorhynchus umbraculum, in the Lower Devonian of the western slope of the Urals, but does not give their description. The Turkestan specimens described by Nalivkin (43, 26) under the name Schuchertella (?) umbraculum differ from our specimens in their short hinge margin, partial deformation of the shell, and in that their ventral valve is more inflated than the dorsal one. This last circumstance, noted twice by the author, together with the presence of a sinus on the ventral valve, gives strong reason to doubt the assignment of the Turkestan specimens to Schlotheim’s species.

For Siberia, the presence of this species was noted by Petz (51, 73) in the Stringocephalus beds of the southern part of Kuzbass, and by Bublichenko (8, 1209) in deposits of southwestern Altai, which this author assigns to the lower part of the Middle Devonian. In neither work is a description of the specimens given, and for this reason these works have not been included in our synonymy. Specimens from the Stringocephalus deposits of the Minusinsk Basin, identified by Stuckenberg as Streptorhynchus crenistria (63, 6), require redetermination.

At our disposal are specimens of S. umbraculum from the Stringocephalus deposits of the Korgon Range (Altai), the fauna of which is in general extremely close to the Lebedyanskaya fauna. In the Lower Devonian deposits of Northern Altai, a form externally very close to the species under consideration, Schuchertella altaica Khalf. (36), is widespread, while in the Upper Devonian of Kuzbass (34, 22) there also occurs Schuchertella chemungensis Conr., externally close to the given species.

It remains to say a few words about the generic assignment of Schlotheim’s species. The presence of fairly well-developed dental plates makes it impossible to assign this species either to Streptorhynchus or to Schuchertella. The commonly practiced assignment of it to the genus Orthotetes is incorrect, since already Girty (18) and Thomas (65) established that this genus is characterized by the presence of a septum in the ventral valve. The median ridge observed in the ventral valve of S. umbraculum between the imprints of the diductors in their anterior part is a structure genetically distinct from a true septum and, according to Thomas’s terminology, may be called a pseudoseptum. “The septum of Orthotetes Fisch. is formed by the fusion of two dental plates and, by virtue of such an origin, is an important organ, the development of which is laid down as early as the time of embryonic development” (66, 265).

Thus, the presence of well-developed divergent dental plates, in the absence of a septum in the ventral valve and with a non-plicate shell surface, fully determines the assignment of Schlotheim’s species to the genus Schellwienella.

Found in a large number of specimens along the Alchedat River.

Schuchertella chemungensis Conr.

(Table II, fig. 15).

1. Schuchertella chemungensis: Khalfina. Upper Devonian of the village of Zharkovsky, p. 22, pl. II, fig. 16; pl. III, figs. 1, 4.

Representatives of this species are numerous in the Upper Devonian of Kuzbass and were characterized in detail by me in the cited work. In the Lebedyan—

in the fauna of Skoki, Schuchertella chemingensis belongs to the rare forms and differs in no way from its Upper Devonian representatives.

Dalmanella eifeliensis Vern.

(Plate II, figs. 16–18).

1. Orthis Eifeliensis: Barrois. Mém. Soc. Géol. Nord, vol. II, p. 225.
2. Orthis Eifeliensis: Davidson. Brit. Foss. Brach., vol. V, pt. I, p. 50, pl. III, fig. 16.
3. Ortis Eifeliensis: Whidborne. Dev. Fauna South Engl., vol. II, p. 145.
4. Orthis Eifeliensis: Sobolev. Dev. beds, prof. G.–S.–V., p. 66 (Synon. ib.).
5. Orthis (Rhipidomella), eifeliensis: Reed. Dev. Fauna North Shan States, p. 81, pl. XIII, figs. 25–26.
6. Dalmanella Eifeliensis: Sobolev. Middle Dev. Kel.–Sain. Ridge, p. 460.
7. Orthis Eifeliensis: Asselbergs. Faune frasn. infér. du bass. Namur, p. 4.
8. Dalmanella Eifeliensis: Quiring. Zusamm. Strophomen. Eifel, S. 121.

This is the most widespread species among the Dalmanellacea of Lebedyanskoye village. Our representatives of this species are quite typical, but in some respects they show considerable variability.

The shell is small, slightly developed in width. The outline of the shell is rounded, indistinctly quadrangular; in the most typical specimens (Plate II, figs. 16 a–b) the greatest width of the shell lies closer to the anterior margin, which gives the shell, to some extent, trapezoidal outlines: the shell narrows toward the posterior margin. In many specimens, however, this widening of the shell toward the anterior margin is very slight. The length of the straight hinge margin equals 0.5 of the width of the shell. The anterior margin is straight or with a slight bend.

The ventral valve is moderately convex. The beak is small, sharp, incurved; the area is low, triangular. From the beak along the median line of the valve there runs a flat, very indistinct elevation, which on the anterior half of the shell becomes smoothed out, giving way to a broad flat depression; sometimes on the middle and anterior parts of the shell there are combined a broad flat depression and, along its middle, an indistinct flat elevation.

The dorsal valve is somewhat less convex. It has a very low triangular straight area. The sinus is distinct, flat, strongly widening toward the anterior margin.

The outer surface of the valves is covered with numerous fine radial ribs, straight near the median line of the valves and arcuately curved on their lateral parts. Their number is about 80 along the margin of the shell (2.5 per 1 mm). The riblets increase in number partly by dichotomy, but chiefly by intercalation. Several orders of riblets can be distinguished: some of them run from the very beak (usually 12–14 in number); these are the largest (thickest) riblets. Near the very beak, riblets of the second order are inserted between them, at first having the appearance of thin striae, but rapidly thickening and, on the anterior half of the valves, reaching the thickness of the riblets of the first order. Farther on, riblets of the third order are inserted, usually considerably thinner than the preceding ones. And finally, near the margin of the valves there appear short and thin striae of the fourth order.

The concentric growth marks are few, coarse, and situated near the margins of the valve. The substance of the shell is punctate.

Inside the ventral valve there are well-developed teeth, supported by short dental plates. The continuation of the latter in the form of a weak ridge surrounds the heart-shaped-oval outlines of the muscle impressions, divided by a median longitudinal septum. The length of the muscular

the area is equal to 0.5 of the shell length. In the dorsal valve there are strong brachiophores and a well-developed simple cardinal process. The latter is supported by a septum reaching the center of the valve. The muscle field is very weakly outlined, rounded-quadrate, four-lobed; it is clearly observed only in very well-preserved specimens. Usual dimensions: length 12 mm, width 15 mm, thickness 7 mm.

Dalmanella eifeliensis is very widely distributed. In the Middle Devonian of Europe and Asia it is one of the most common forms. Asselberghs (op. cit.) indicates the presence of this species in the Lower Frasnian deposits of Namur. The form mentioned under the name Dalmanella sp. (33; 9) in my summary of the Lower Frasnian brachiopods of the Kuzbass and coming from Abramovskii aul (southern margin of the basin) belongs to the species Dalmanella eifeliensis. Extremely close (if not identical) is D. superstes Hall and Cl. from the Upper Devonian of North America (Chemung group, N. Y.). Very close forms also occur in the Lower Devonian (for example, Dalmanella ellsworthi Tansey from Bailey Is., Missouri).

In the vicinity of the village of Lebedyanskoye, specimens of this species occur in very large numbers in the outcrops along the Alchedat River above the quarries and along the Kitat River below the cattle yard; at other localities D. eifeliensis is rare.

Dalmanella eifeliensis Vern. var. subtetragona Gürich.

(Table II, figs. 20 a—c.)

1. Orthis (Rhipidomella) subtetragona: Gürich. Palaeoz. Poln. Mittelgebirg., S. 239 Taf. X, Fig. 7.
2. Orthis subtetragona: Sobolev. Dev. dep. prof. G. S.-V., p. 65.
3. Dalmanella subtetragona: Sobolev. Middle Dev. Kel. Sand. Reg., p. 458.

Along with typical D. eifeliensis, our collection contains a form differing from it only in the less rounded outlines of the shell. In this form, the greatest width of the shell usually coincides with the middle of its length, and is not shifted toward the anterior margin, as in D. eifeliensis. Therefore the shell has the outline of a regular rectangle with rounded corners. More rarely, a slight narrowing of the shell toward the cardinal margin is observed (as in D. eifeliensis). In all other respects there is complete similarity with typical D. eifeliensis Vern.

This form is connected by all transitions with Verneuil’s species, and I cannot regard it otherwise than as a variety of the latter. It shows the greatest similarity to Dalmanella subtetragona Gür., which differs from D. eifeliensis, as is known, only in its less rounded outlines (21, 240, 241). It must be noted, however, that the Lebedyanskoye representatives both of typical D. eifeliensis and of the variety subtetragona differ slightly from the European ones by the less distinctly expressed trapezoidal outline of the shell. In this respect they are quite analogous to the Burmese D. eifeliensis described by Reed (55; 81). For the same reason, some specimens of the variety described, in the outlines of the shell, stand closer to D. tetragona Roem. than to var. subtetragona Gür. From Roemer’s species, however, they differ substantially by the shorter cardinal margin and by the coarser ribbing.

Dimensions:

length	width	thickness
12.5	15	7
12.5	15.5	7

It occurs together with the typical form along the Alchedat River, above the quarries.

Dalmanella sibirica n. sp.

(Plate II, figs. 19 a—b; Plate III, figs. 24 a—d, 25, 26).

The shell is developed in width, with a rounded-quadrangular or transversely elliptical outline. The greatest width is in the middle. In large specimens the hinge margin reaches \(2/3\) of the shell width, and in young specimens \(1/2\) of the width. Both valves are moderately and approximately equally convex; the greatest convexity is in the middle.

The ventral valve has a moderately high, concave area. The width of the delthyrium is \(1/5\)—\(1/6\) of the length of the base of the area. From the beak to the anterior margin there passes a very flat median elevation, bounded by weak depressions. The area of the dorsal valve is very low, completely straight. The sinus on the dorsal valve is distinctly expressed.

The sculpture consists of thin rounded ribs, increasing in number by intercalation; the later-appearing ribs are thinner than those formed earlier. Growth marks are few, coarse, and are situated near the shell margins.

Fig. 3. Dalmanella sibirica n. sp. Ventral valve from the inner side.

Inside the ventral valve there are teeth supported by dental plates; the continuations of the latter, in the form of a raised ridge, surround small heart-shaped muscular impressions. A very characteristic detail is the articulation of the tooth and dental plate: the latter, adjoining the teeth, bifurcates; thus the tooth rests upon a small fork.

In the dorsal valve there are powerful, short brachiophores, a very weakly developed trilobed cardinal process, and large, subquadrate, quadrilobate muscular impressions.

Dimensions of our specimens:

length	width	thickness
24	30	12
21.5	27	10
17.5	23	8.5
13	16	5
9	11.5	3.5

The species described, in many respects, shows complete similarity to Dalmanella polonica Sob. from the Middle Devonian of Poland: the detailed description of this species given by Sobolev (62, 461) in many details corresponds fully to our species. The differences between these species consist in the following:

In D. sibirica the shell is convex more uniformly, with the greatest convexity in the middle of the valves, whereas in D. polonica the greatest convexity lies near the hinge margin, and at the frontal margin the valves are only “weakly convex.” The growth marks in D. polonica are more sharply expressed and more numerous. Finally, a specific feature of D. sibirica is the fork-like bifurcation of the dental plates noted above. The author was able to observe this character especially clearly on internal molds of D. sibirica from the Altaian Middle Devonian deposits, coeval with the Lebedyanskian Devonian.

Young specimens of D. sibirica strongly resemble specimens of Rhipidomella vanuxemi Hall occurring together with them, from which they differ by the almost regular elliptical outline of the shell.

D. sibirica has been obtained in a considerable number of specimens from the R. Agachedat, upstream of the quarry, and in a considerably smaller number from the northern outcrops of the Lebedyansk Devonian along the R. Kitat.

Delmanella cf. tioga Hall.

One slightly damaged specimen shows a great resemblance to the species Dalmanella tioga Hall. It differs from D. sibirica in the different outline of the shell and in the sharper, more acute saddle of the ventral valve. Precise determination is difficult because of the insufficiency of the material.

The specimen comes from the northern exposures of the Lebedyansk Devonian on the right bank of the R. Kitat.

Rhipidomella vanuxemi Hall.

(Plate II, fig. 21 a-b).

1. Orthis Vanuxemi: Hall. Pal. N. Y., vol. IV, p. 47, pl. VI, fig. 3 a—r.
2. Rhipidomella Vanuxemi: Kindle. Onondaga Fauna, p. 79, pl. V, figs. 17—19.
3. Rhipidomella Vanuxemi: Prosser and Kindle. Brach. Middle Dev. Maryland, p. 165, pl. XIII, figs. 26—29. Synonymy ibidem.
4. Rhipidomella Vanuxemi: Clarke and Swartz. Brach. Upp. Dev. Maryland; p. 572.
   Comp.: Rhipidomella Hamoni Rouault. Rhipidomella Michelini Vern. (non Leveillé).

The shell is rounded in outline, with a short straight hinge margin. The greatest width is closer to the anterior margin; the shell narrows strongly toward the hinge margin—much more distinctly than in Dalmanella eifeliensis. But in general, in the outlines of the shells of these two species there is considerable similarity.

The ventral valve as a whole is weakly convex; the greatest convexity is in the umbonal part; toward the anterior margin the shell becomes flat and even depressed. The beak is small, sharp, straight, and slightly raised above the hinge line.

The dorsal valve is somewhat more convex than the ventral; the beak of this valve is still smaller, the area still lower. Along the median line of the valve there runs a very weak sinus-like depression, analogous to that in D. eifeliensis, but flatter and less broad.

The sculpture consists of numerous fine ribs, multiplying by dichotomy and intercalation. Growth marks are not numerous. Concentric striation is not visible on our specimens (the preservation of the external surface is poor).

Dimensions:	length	width	thickness
	16	17.5	6
	15	17	5.5
	10	11	4
	15	17	5.5

Rh. vanuxemi is distributed in the Middle and Upper Devonian of North America. Our specimens show complete similarity to the Middle Devonian New York representatives of this species (23, pl. VI, fig. 3 a—g); the Maryland specimens of Rh. vanuxemi (see synonymy) apparently differ in the complete absence of a sinus on the dorsal valve. Of the European species, the closest to Rh. vanuxemi (apparently identical) are Rh. hamoni Rouault and Rh. michelini Vern. Oehlert considered (44, 48) Rh. vanuxemi a synonym of Rh. hamoni. Rh. leucosia Hall and Rh. subcordiformis Kayser differ ...

heart-shaped outline of the shell: the latter narrows more strongly toward the beak than in Rh. vanuxemi.

In our collection Rh. vanuxemi is most similar (in external characters) to Dalmanella eifeliensis, with which it also occurs together. The similarity lies in the outlines of the shell, the short hinge margin, and the character of the sculpture. The differences are as follows: the shell of D. eifeliensis is much more inflated; the ratio of width to thickness in this species is about 2, whereas in Rh. vanuxemi it is about 3. The beak of the ventral valve in Rh. vanuxemi is sharp and straight; in D. eifeliensis it is curved. The depression near the anterior margin on the ventral valve of Rh. vanuxemi is much broader, so that it no longer has the character of a sinus (as in D. eifeliensis), but has the character of a general depression of the ventral valve in its anterior half. The ventral valve of Rhipidomella vanuxemi lacks the median elevation present in the umbonal part of the valve in D. eifeliensis. Direct comparison of specimens of these two species makes it easy to distinguish them.

Rh. vanuxemi was collected together with D. eifeliensis from the Alchedat River, above the quarry.

Schizophoria striatula Schloth.

(Table III, figs. 27, 28, 29).

This common and widely distributed species is represented in our collections by typical specimens and belongs to the most widespread forms in the Lebedyansk fauna.

Kayserella ramosa n. sp.

(Table III, fig. 30 a—c).

A small, rounded, plano-convex shell with a long, straight hinge margin. The greatest width coincides with the middle of the shell; the length of the hinge margin reaches ¾ of the greatest width. The lateral and anterior margins are smoothly rounded.

The ventral valve is moderately convex. The beak is small, sharp, not projecting strongly above the hinge line, and slightly curved. The area is low, triangular; its height amounts to 0.2 of the length of its base. From the beak begins a low and flat, but quite clearly expressed, median elevation, reaching in width near the anterior margin almost 0.5 of the greatest width of the shell. It is bounded by distinct narrow furrows.

The dorsal valve is flat. The beak is very small. The area is perfectly straight, considerably lower than on the ventral valve (its height is equal to 1 mm). Along the median line of the valve runs a broad, distinct sinus.

The sculpture consists of thin radial ribs, straight on the fold and in the sinus and bow-like deflected from the plane of symmetry on the lateral parts of the shell. The ribs are grouped into distinct bundles, especially clearly expressed on the lateral parts of the valves. The number of such bundles is 7–8 on each side of the fold and the sinus. The number of ribs in the bundles is 4–5 in each, except for the outermost bundles (adjacent to the cardinal angles), in which there are only 2–3 riblets. On the fold and in the sinus the fasciculate arrangement of the ribs is not sharply expressed; their simple dichotomy predominates.

In addition to several rather sharp growth marks, there was apparently a fine concentric striation, traces of which are discernible in places with a hand lens in the intervals between the ribs.

Dimensions: width—15.5; length—13; thickness—5.

The species described differs sharply from the well-known R. lepida Kays. and K. lepidaeformis Gür. in the fasciculate arrangement of the ribs.

Two specimens of K. ramosa were found along the Alchedat River, near the cemetery.

Uncinulus korovini n. sp.

(Pl. III, figs. 31 a—b, 32 a—b, 33 a—b, 34).

This is one of the most widespread forms in the fauna of the Lebedyanskoye Middle Devonian. Representatives of this genus show considerable variability in external characters.

The shell is of medium size, strongly inequivalve, inflated, with a rounded-pentagonal outline. The width is somewhat greater than the length. The greatest convexity is near the anterior margin. The sides of the shell are perpendicular to the surface of the ventral valve. The saddle and sinus are considerably developed only near the anterior margin.

The ventral valve is very weakly convex, almost flat. Near the anterior and lateral margins its surface forms a sharp geniculate bend toward the dorsal valve. The beak is not especially high, sharp. The apical angle is about 115°. The sinus in the apical and umbonal parts is not noticeable; near the anterior margin it is a rather broad, shallow depression with a flat bottom. The tongue is high, flat, with parallel lateral margins. The denticles of the valve suture are not sharp. Inside the ventral valve there are teeth supported by well-developed dental plates. The latter are reflected on the external surface in the form of two “cracks,” diverging from the beak at an angle of 46°—50°.

The dorsal valve is considerably more convex. The saddle, completely unexpressed in the umbonal part, near the anterior margin is a considerable flat-topped elevation. Inside the dorsal valve there is a well-developed—high and long—thin septum. In the rostral region the septum bifurcates, forming a septalium. The cardinal process is bilobed.

The sculpture consists of radial flat-rounded ribs separated by narrow interspaces. The ribs are distinctly expressed near the margins of the shell, but gradually disappear in the umbonal part; the ribs lying on the saddle and in the sinus persist longer than the others, but even they never reach the beak. Near the very margins of the shell longitudinal furrows appear on the ribs (one on each rib). The number of median ribs (lying within the saddle and sinus) is usually 4, rather often 3, and rarely 5 on each valve. Sometimes the number of ribs on the saddle is one fewer than in the sinus. There are no parietal ribs. On the lateral parts of the valves there are 6—8, rarely 9 ribs on each side of the saddle and sinus. According to Oehlert’s formula the ribbing of our species is expressed as follows: m. r. \(\frac{3—5}{3—5}\); p. r. 0; l. r. 6—8. In the case of an odd number of ribs in the sinus, often the middle one is sharper and begins nearer the beak than the others (Pl. III, fig. 33 a).

The dimensions of our specimens vary within the following limits:

length	width	thickness
16	16	12
11.5	12.5	9
18	22	15

The form closest to the species described above is Uncinulus (?) subsignatus Reed from the Lower Middle Devonian of Burma (55, 93). Because Reed’s species has a higher beak and a somewhat smaller apical angle, the outline of the shell in that species is different from ours, approaching the outlines characteristic of representatives of the genus Camarotoechia Hall and Clarke. The ribs, as well as the saddle and sinus in Uncinulus subsignatus, can be traced almost to the beak, in contrast to what we have in U. korovini. The shell in U. subsignatus is less inflated.

In conclusion, a few words on the generic characters. The form of the shell, the character of the ribbing, and the presence in the dorsal valve of a median septum and a hinge process—all this fully corresponds to the diagnostic features of the genus Uncinulus Bayle. But, alongside this, in the species U. korovini there is observed a septalium, characteristic of the genera Camarotoechia H. et C., Wilsonia Kayser, Liorhynchus Hall, Pugnoides Weller, and Patyphorhynchus Weller, which differ from the genus Uncinulus by the absence of a hinge process. On the other hand, I have not found in the literature available to me any indications of the presence of a septalium in the genus Uncinulus. In the monograph by Hall and Clarke (24, pl. LVIII, figs. 17, 24), figures are given of representatives of the genus Uncinulus in which, despite the presence of a hinge process, the septalium is absent. However, the joint presence of these two elements is possible, and it is shown in the same monograph (l. c., pl. LVIII, figs. 36, 37) for the genus Plethorhyncha H. et C. And although this combination of elements of the internal skeleton is not usual for the genus Uncinulus, it does not seem to me that its presence is sufficient for establishing a new genus or even subgenus.

Representatives of the genus Uncinulus are widely distributed in the Lower Devonian and are rare in the Middle Devonian.

Specimens of U. korovini occur in enormous numbers along the Alchedat River between the mouth of the Kamenushka spring and the cemetery. They are less numerous along the Alchedat River opposite the eastern end of the village of Lebedyanskoye. In the form of only single specimens, U. korovini has been obtained from outcrops along the Kitat River, near the mill and below the cattle yard.

Uncinulus (?) subsignatus Reed.

(Table III, fig. 36 a—c.)

1. Rhynchonella (Camarotoechia) subsignata: Reed. Dev. Faunas of the North Shan States, p. 93, pl. XIV, figs. 19—23.

Two specimens in our collection belong to this species, both somewhat damaged. They differ from the preceding species by a stronger development of ribbing. The median ribs begin at the beak, the lateral ones in its immediate vicinity. In the sinus of one specimen there are 4 ribs; in the sinus of the other, 5, with the middle one more developed than the others. The shell, judging from the better-preserved specimen, is less inflated than in U. korovini. The sinus begins near the beak and is more strongly developed than in U. korovini. In the dorsal valve there is a septum. The presence of a hinge process has not been established, which is why the generic assignment is accompanied by a question mark.

Our specimens show complete similarity to the specimens described by Reed in the cited work. The specimens characterized were obtained from the Alchedat River, near the cemetery.

Uncinulus (?) concentricus n. sp.

(Pl. III, figs. 35 a—b)

One specimen in our collection, similar in shell form to U. korovini, considerably exceeds the representatives of this species in size and possesses a number of specific features.

The shell is strongly inflated, inequivalved. The ratio of width to length is close to 1.

The ventral valve is slightly convex; its surface at the lateral and anterior margins forms a sharp geniculate bend toward the dorsal valve, characteristic of representatives of the genus Uncinulus and forms close to it. The beak is low, sharp, slightly incurved. The sinus is not at all expressed near the beak. At half the distance between the beak and the anterior margin it has the character of a broad, completely flat depression, which farther on, as it approaches the frontal margin, gradually widens and deepens. In general, the sinus is moderately developed. The tongue of the sinus is completely flat, high, with parallel lateral sides. The dorsal valve is strongly inflated. The saddle is damaged; it is difficult to judge its character.

The sculpture of the external surface consists of sharp radial ribs beginning from the beak. The ribs are rather high, rounded, and only near the anterior margin become flat; a longitudinal groove appears on them. Most of the ribs are simple; some dichotomize (once). The intervals between the ribs have the character of narrow, sharp furrows. Four median ribs depart from the beak; two of them bifurcate dichotomously at a short distance from the beak. Thus, there are 6 ribs in the sinus. The parietal ribs are present singly on each side. There are more than 10 lateral ribs (apparently 12–13) on each side of the sinus.

Growth marks are coarse, rare. In addition to them there is also the finest concentric striation, discernible with the naked eye and clearly visible under a hand lens, but only on a fully preserved external surface. This striation consists of fine concentric riblets, not of lamellar growth marks, such as are characteristic, for example, of many Athyridae. Over a length of 1 mm there are 7–8 of these concentric riblets.

Details of the internal skeleton have not been established.

The described specimen was found on the Alchedat River above the quarry. Other representatives of the genus Uncinulus were not found together with it.

Cryptonella planirostra Hall.

(Pl. III, figs. 37 a—b, 38 a—c).

1. Cryptonella planirostra: Hall. Pal. N. Y., v. IV, p. 395, pl. LXI, figs. 9—21.
2. Cryptonella planirostra: Hall and Clarke. Pal. N. Y., v. VIII, pt. II, p. 268, pl. LXXX, figs. 5—10.
3. Cryptonella planirostris: Schuchert. Syn. Amer. foss. Brach., p. 194.
4. Cryptonella planirostra: Petr. Mater. on the knowledge of the fauna of the Devonian deposits of Kuzb., p. 173, pl. V, fig. 42.
5. Cryptonella planirostra: Nalivkin. Brachiopods of Turkestan, p. 93, pl. VII, fig. 22.

There are three specimens which I assign to this species. Their dimensions are:

length	width	thickness
15.5	12.5	8.5
9.0	8.5	5.0
6.0	5.5	—

The shell is of a rounded-pentagonal outline. In the largest specimen the anterior margin is straight; in the smaller ones it is broadly rounded. The ventral valve is somewhat more convex than the dorsal. There is no fold or sinus. The moderately high, slightly incurved beak of the ventral valve is provided with a small round foramen; a rather large area is visible, indistinctly bounded by two lines running from the beak to the ends of the hinge line, with rounded edges. The surface of the valves is smooth; only faint growth marks are present. The shell substance is finely punctate.

Specimens of the species C. planirostra show considerable variability in the outline of the shell, the anterior margin becoming straight only in mature growth stages (see, for example, the figures in the cited work of Hall). A great similarity in external characters is also known among certain species of the closely related genera Cryptonella Hall, Eunella H. & C., and Cranaena H. & C. Therefore, the assignment of the Siberian specimens, not investigated as to their internal structure, to the species C. planirostra must for the time being be regarded as provisional.

C. planirostra occurs in North America in Middle Devonian deposits. Petz cites this species from the Upper Devonian deposits of the Kuzbass; Nalivkin—from the Neodevonian of Fergana.

The Lebedyanskoye specimens described above were obtained from the R. Kamenushka.

Cryptonella (?) rhomboidea n. sp.

(Table VII, fig. 69 a—d).

A small shell, developed in width, of subrhomboidal outline. The ratio of width to length is 1.2. The apical angle is 105°.

The ventral valve is more convex than the dorsal. The greatest convexity of the valves is in the middle. The beak of the ventral valve is small, incurved; the beaks of both valves are in contact. The area is not visible. Sinus and fold are absent, but the anterior margin is slightly bent toward the dorsal valve.

The outer surface of the valves is completely smooth. Under a strong lens the rhombic porosity of the shell substance is clearly visible (a quite similar structure is figured by Whidborn’a—75, pl. XI, figs. 1a, 2b, 4b).

Dimensions:

length	width	thickness
11.5	14	7

In our collection there is one specimen of this species, for which reason the internal structure remains unclarified, and the generic determination must not be regarded as final.

By the characteristic transversely rhombic outline of the shell, our specimen recalls certain American species of the genus Nucleospira Hall (cf. 22, pl. XXVIIIb, figs. 12 c—d), in which the “surface of shell finely and beautifully punctate”; but this punctation in the genus Nucleospira has a different character and a different origin than the rhombic porosity of the shell of our specimen.

Cryptonella cf. jucunda Hall.

One damaged specimen differs sharply from the preceding species in the outlines of the shell. Despite the considerable deformation of this specimen, it can nevertheless be seen that the shell is developed in width and has subtriangular outlines with a broadly rounded anterior margin. Our specimen is most similar to Cryptonella (?) jucunda Hall (23, 390), but its precise determination is impossible.

C. jucunda in North America occurs in D₂. Our specimen was found together with C. planirostra.

Trigeria (?) lata n. sp.

(Table IV, figs. 39 a—c).

The shell is large, subtriangular in outline; its greatest width is near the frontal margin. The apical angle is about 75°. The anterior margin is broadly rounded.

The ventral valve is more convex than the dorsal. The fold and sinus are entirely absent. The beak of the ventral valve is long, strongly curved; its beak is pressed against the umbo of the dorsal valve, so that the foramen and delthyrium are not visible.

The sculpture consists of flat, rather broad radial folds, numbering 12 on the ventral valve and 14 on the dorsal valve. These folds are very weak and are noticeable only near the anterior margin; at a distance of 8—12 mm from the latter they are already indistinguishable. In addition to them, on the anterior half of the valves there are fine, rather numerous concentric lines, not of a lamellar character. The umbonal parts of the valves are completely smooth.

The structure of the shell substance is punctate.

Dimensions of the single specimen:

width—25; length—28; thickness—16.5.

The internal structure of this specimen is unknown. By its external characters it comes closest to the genus Trigeria Bayle. From all known species of this genus, as is evident from the description given above, it is entirely distinct.

The specimen was supplied by Yanishevsky; the label reads: “vicinity of the village of Lebedyanskoye.”

Spirifer cabedanus Vern. et Arch.

(Table IV, figs. 40, 41 a—b).

1. Spirifer cabedanus: Verneuil et Archiac. Bull. Soc. Géol. Fr. vol. II, sér VII, p. 473, pl. XV, fig. 8.
2. Spirifer cabedanus: Barrois. Mém. Soc. Géol. du Nord, vol. II, p. 249, pl. X. fig. 2-3.
3. Spirifer cabedanus: Barrois. Annales Soc. Géol. du Nord, XIII, p. 88.
4. Spirifer cebedanus: Oehlert. Bull. Soc. Géol. Fr., sér. III, vol. XXIV, p. 872, pl. XXVIII, fig. 13—16.
5. Spirifer cabedanus: Petz. Mater. k pozn. fauny dev. otl. etc., p. 83, tabl. IV, fig. 12.
6. Spirifer cabedanus: Mansuy. Contrib. a la carte géol. Indo-China, p. 40, pl. IX, fig. 3—5.

A characterization of the Siberian representatives of this species was given by Petz in the cited work. To this characterization I can add that in the Lebedyanskoye Devonian there occur both specimens with slightly rounded cardinal angles and specimens in which the greatest width of the shell coincides with the hinge margin.

The Lebedyanskoye specimens of Sp. cabedanus show the closest similarity to the Spanish representatives of this species figured by Oehlert. Isolated dorsal valves of S. cabedanus are difficult to distinguish from those of Spirifer bouchardi Murch.; spirifers of the S. bouchardi group, widely distributed in the Lower Frasnian deposits of the Kuzbass, differ from S. cabedanus in the very low area (with parallel margins) of the ventral valve and in the greater development of the shell in width. In the Lower Frasnian deposits of the Abramovskiy mine (southern margin of the Kuzbass) there occurs Spirifer acutulus, very close to the species under consideration.

mihi; the latter differs from S. cabedanus in the pointed terminations of the cardinal angles, a flat sinus, and the straight area of the ventral valve.

In Western Europe S. cabedanus is distributed from the Couvinian to the Frasnian deposits inclusive (4, 502). The same is its distribution in Asia as well: in the Kuzbass Petz indicates S. cabedanus from the Frasnian deposits of Abramovka, while in Indo-China Mansuy cites it from shales with Spirifer tonkinensis, which by that author were assigned to the Upper Silurian, but according to later investigations are of Eifelian age (19, 197).

S. cabedanus has been delivered in a considerable number of specimens from the Anchedat River, near the mouth of the Kamenushka Creek.

Spirifer cf. argentarius Meek.

(Table III, fig. 42).

The collection contains one specimen of a spirifer close to the preceding species, but differing from it in having a smooth sinus (with the presence of a deep groove on the saddle).

The shell is of medium size, slightly developed in width (the ears in our specimen are broken off). The ventral valve is strongly convex, with a high triangular, strongly concave area. The dorsal valve is moderately convex, with a linear area. On the ventral valve there is a well-developed sinus beginning at the very beak; the profile of the sinus is rounded-angular. The sinus is smooth; its width is equal to the width of six adjacent ribs. The saddle of the dorsal valve is moderately high, divided by a deep median groove; its width is equal to the width of the sinus. On each side of the saddle and sinus there are 10–12 simple rounded costellae. The surface of the shell is covered with dense, fine concentric growth marks, which are preserved only in places, in the spaces between the ribs.

Closest to our specimen is the American Spirifer argentarius Meek, possessing only a more smoothly rounded profile of the sinus. Walcott (71, 138) unites S. argentarius with Spirifer pinonensis Meek; the latter, however, has larger dimensions, broad, flat ribs, and an almost unsegmented saddle, thus showing substantial differences from our specimen. It is also necessary to note the great resemblance of the latter to young individuals of Spirif. martianoffi Stuck., but in that species the depression on the saddle is apparently always weakly expressed, whereas in our specimen the saddle appears as if consisting of two large ribs owing to the presence of a sharp and deep median groove.

Spirifer argentarius in North America (Nevada) passes through the whole Devonian. In the Lebedyanskian Devonian the specimen described was found together with S. cabedanus.

Spirifer undifer Roem.

1. Spirifer undifer: Petz. Materials toward the Knowledge of the Fauna of the Devonian Deposits, etc., p. 108 (Syn. ibidem).

This well-known species is represented in the collection described by two specimens. The variability of representatives of this species with respect to external characters is also known. Our specimens belong to the type characterized by an almost isometric shell of circular outline, with fairly sharp, not broad ribs, a shallow sinus, and a flat-topped saddle.

In the Middle Devonian deposits of Siberia, S. undifer is widely distributed, but in the Lebedyanskian Devonian it is very rare. In the Urals and in Turkestan it is known from the lower Neo-Devonian. Specimens of this species were found by M. K. Korovin along the Alchedat River.

Spirifer martianoffi Stuck.

(Table IV, figs. 43a—d).

1. Spirifer Martianoffi: Stuckenberg. Mater. z. Kenntn. d. Fauna Dev. Ablag. Sibir., S. 8, Taf. IV, Fig. 9—13.

The shell is of considerable size, extended in width, and semi-elliptical in outline. The hinge margin corresponds to the greatest width of the shell. The valves are moderately and equally convex.

The beak of the ventral valve is low, slightly incurved. The moderately high area has indistinctly triangular outlines. The height of the area is 6 mm, which constitutes \(1/9\) of the length of the hinge margin. On the area there is horizontal and vertical striation. The open delthyrium has the form of a broad triangle; the width of the delthyrium is 10 mm (5.5 of the length of the hinge line). The sinus begins at the beak, is moderately broad and deep, with a smoothly rounded bottom; the width of the sinus along the frontal margin corresponds to the width of seven adjacent ribs. The tongue is low, gently arcuate; its height is less than \(1/2\) the width of the sinus. There are no radial ribs in the sinus.

The area of the dorsal valve is bounded by parallel margins; its height is 1 mm. The fold is distinctly expressed, beginning from the very beak, moderately broad and high, with a flat-rounded top, along which a slight depression passes. Its width is equal to the width of the sinus.

On each side of the fold and sinus there are up to 16 radial ribs. The ribs are simple, distinct, rounded; the intervals between them are narrower and sharp. Dense concentric growth marks, characteristic of the group Spirifer martianoffi Stuck., cover the surface of the shell. From typical Minusinsk representatives of this species our specimen differs in the lower area of the ventral valve; on this basis it might perhaps be more correct to distinguish it as a separate variety.

The specimen comes from the Alchedat River, near the cemetery.

Spirifer n. sp.

The collection contains one fragment of a rather large ventral valve. The beak is broken off, but it was evidently incurved. The area is high, triangular, concave, covered with horizontal and vertical (?) striation. So insignificant a part of the sinus has been preserved that one can say of it only that it is smooth. On the sufficiently completely preserved lateral part of the valve there are 13 simple, distinct radial ribs. The character of the ribs is as follows: only at the very beak are they rounded; along the rest of their extent they are completely flat. The intervals between them are likewise flat. The intervals between the ribs are narrower than the ribs themselves: the ribs adjacent to the sinus have, near the margin of the valve, a width of 1.5 mm, whereas the intervals between them are already 1 mm.

The specimen was found along the Kamenushka River (near its mouth).

Group Spirifer cheehiel Kon.

Among the most interesting groups of fossils of the Siberian Paleozoic is the widely distributed in the Middle Devonian and rather diverse association of species of the genus Spirifer, grouped around Spirifer cheehiel Kon. This latter species was established by Koninck as early as 1840 (38, 410), on the basis of the study of only four specimens that had been in

at the disposal of this investigator. In 1883 Kayser described (30, 87) one specimen of Spirifer cheehiel, brought from China by Richthofen’s expedition. Thus, for a long time this interesting form was known to paleontologists only from a very few specimens, obtained more or less by chance. Only Stuckenberg, in 1886, gave a new, fairly detailed description of Spirifer cheehiel, based on the study of abundant material (85 specimens) originating from the Minusinsk depression (63, 10). This author established a new variety of Koninck’s species, distinguished by considerable development in width and named var. alata. And finally, in 1927, Korovin, in the faunal list from Lebedyanskoye, indicated a new form—Spirifer cheehiel Kon. var. mesoloba n. var. (39, 35). This exhausts all the literary data on the group of Spirifer cheehiel available to me¹.

The group Spirifer cheehiel is extremely widely distributed in Siberia. At my disposal there is extensive material originating from the Kuznetsk Basin, the Minusinsk depression, and also from Northern, Central, and Southern Altai. Everywhere this group occupies a quite definite stratigraphic position (upper part of $D_2^2$), being for Siberia the stratigraphic analogue of Stringocephalus burtini Defr. In the collection from the village of Lebedyanskoye there are more than two hundred specimens of spirifers of the group Spirifer cheehiel. Familiarity with all the collections at my disposal has shown that in the present case we are dealing not with a single species, but with a whole series of closely related forms.

The general form of the shell and the character of the sculpture (smooth sulcus and sinus, broad folds on the wings, and lamellar growth marks provided with small papillae) permit us to assign our forms to that group of spirifers to which the name Hysterolites Schl. is presently applied.

While assigning the group Spirifer cheehiel to the subgenus Hysterolites, I nevertheless consider it necessary to note that the spirifers of this group form so close an association in morphological, stratigraphic, and geographic respects that it might perhaps be more correct to separate them into a special subgenus. As for the term “Hysterolites” itself, the assignment of this ancient name to the group of Devonian spirifers in general must be regarded as rather artificial, since the original meaning of this term was very broad and indefinite, and even Hall and Clarke cautioned in their time against its use (see 24, pt. 1, p. 213).

Intending in the near future to devote special attention to the group Spirifer cheehiel², in the present article I confine myself only to a detailed description of its Lebedyanskoye representatives.

Spirifer (Hysterolites) cheehiel Kon. typ.

(Pl. IV, figs. 44 a—d, 45, 46, 47; pl. V, figs. 53, 55).

? 1846. Spirifer Cheehiel: Koninck. Bull. Acad. de Belg., vol. XIII, p. 410, pl. 2, 1.
1853. Spirifer Cheehiel: Davidson. Quart. Journ. of the Geol. Soc., p. 338, pl. XV, fig. 17.
1883. Spirifer Cheehiel: Kayser. Dev. Verstein. aus China, S. 87, Taf. XI, Fig. 2.
1886. Spirifer Cheehiel: Stuckenberg. Mem. Acad. Sciences. SPB. XXXIV, S. 9, Taf. 1, Fig. 4; Taf. 2, Fig. 2—7.

This is a form rather variable in its external characters, possessing a shell strongly developed in width. The outlines of the shell are trapezoidal, subtriangular, or semi-elliptical. The hinge margin corresponds to the greatest width of the shell; the cardinal angles in most cases are drawn out into well-developed ears, usually broken off. The ratio of shell width to length varies within broad limits; in general it is greater in large specimens and smaller in young ones.

The area of the ventral valve is well developed along the entire hinge line. In specimens moderately elongated in width, it has rather clear triangular outlines, although with a very large ratio of the length of its base to its height. In specimens approaching the variety alata, only near the plane of symmetry of the shell does the area have triangular outlines; throughout the rest of its extent it is bounded by parallel margins, the distance between which (the height of the area), in fully adult individuals, reaches 5–7 mm. On the area a fine vertical and horizontal striation is distinctly visible. The area of the dorsal valve is very low, usually with parallel margins, more rarely with the outlines of a triangle strongly elongated along its base; its height usually does not exceed 1–1.5 mm, i.e., the area of the ventral valve is 5–6 times higher than the area of the dorsal valve. The areas of the dorsal and ventral valves form a dihedral angle of 50°–70°.

The delthyrium has the form of a broad triangle, the length of whose base is almost twice its height. In the upper part the delthyrium is covered by an arch-shaped pseudodeltidium.

The sinus begins from the very beak, is quite distinctly expressed; its sides are smooth, the floor in young individuals is regularly rounded, in adults it becomes flat. The tongue of the sinus is high, arc-shaped; its height equals half the width of the sinus near the anterior margin, or somewhat more. The width of the sinus near the anterior margin is equal to the width of 4–5 adjacent ribs.

The fold likewise begins from the very beak of the valve, is high, and distinctly bounded. Its summit in typical forms is rounded; when the fold becomes somewhat sharp-crested, the form approaches the appearance of Hysterolites bidevexus (see below).

On each side of the fold and sinus there are 6–8, more rarely 9–10, flatly rounded, broad radial plications, separated by less broad interspaces. The entire surface of the shell is covered with dense concentric growth marks of a lamellar character; the width of an individual lamella is very small: 20–30 lamellae fit into one centimeter. Some of the growth marks are expressed more sharply than others; this is more often observed near the margins of the shell. With good preservation of the outer layer of the shell, small papillae may be seen along the margins of the growth lamellae; on a somewhat worn shell surface these papillae give the impression of the finest interrupted radial striae; usually, however, they are not preserved at all.

In assigning the specimens described above to the species Spirifer cheehiel Kon., I base this on their identity with the specimens of Kayser and Stuckenberg. The illustration given by Kayser gives a general idea of the shell of Spirifer (Hysterolites) cheehiel, but the character of the sculpture in this figure is not accurately conveyed (30, pl. XI, fig. 2c–e), especially on the dorsal valve: the ribs are too broad and the interspaces between them narrow and sharp. I have no opportunity to consult directly the work of Koninck, in which the first description of the species under consideration was given. But Kayser (loc. cit., pl. XI, fig. 2a–b) and Grabau (19, p. 162, fig. 106) provide copies of the illustration of Spirifer cheehiel given by the author of this species.

If only this old illustration is sufficiently accurate, then one may say with confidence that Koninck’s specimen differs from the specimens of Kayser and Stuckenberg, and consequently also from the Lebedyanka specimens described above. The differences are as follows: the dorsal valve in Koninck’s specimen (judging from the illustration) is almost flat; the pseudodeltidium is large, covering almost the entire delthyrium; the spondylium has a completely peculiar structure—near the anterior margin, on the sides of the spondylium, there are two longitudinal depressions, owing to which the spondylium consists, as it were, of three parts, of three broad folds. Therefore, it may be that the identification of our Lebedyanka specimens with Koninck’s species is incorrect, but this means that the validity of assigning to this species the specimens of Kayser and Stuckenberg must also be checked; I do not have sufficient material to resolve this question (Koninck’s paper and Grabau’s new work on the Devonian brachiopods of China). With this reservation I shall henceforth use the name Spirifer (Hysterolites) cheehiel Kon.

The dimensions of this species in the Lebedyanka Devonian vary within the widest limits, for example:

length	width	height	height of the area, ventral valve
40	~100	29	5.5
45	~99	35	6.5
48	~106	41	7.0
45	90	—	7.0
29	50	24	4
23	~42	17	3
17	30	12	2.5
13	23	9	—
9	~18	—	—

Among representatives of the subgenus Hysterolites in the Lebedyanka Devonian, the form described is the most widespread and is universally developed.

Spirifer (Hysterolites) cheehiel Kon., var. alata Stuck.

(Table V, fig. 56).

Stuckenberg (63, 11) assigns to the varieties alata those forms in which the ratio of width to length is equal to two or more. Examination of the extensive Lebedyanka material leads me to think that the normal (typical) form Spirifer cheehiel, in the young stages of growth, has a ratio of shell width to length of less than two, while in the adult condition this ratio, as a rule, reaches two, even two and a half. To separate adult specimens of one species into a special variety is, of course, not possible.

However, in our collection there are, as rare forms, large specimens of the species Spirifer cheehiel in which the width of the shell exceeds the length by three, or almost three, times. Thus, the specimen illustrated in fig. 56, table 5, has a width of 122 mm and a length of 42 mm. For such forms, more than usually developed in width, I retain the name alata, preserving for them the status of a variety, since in all other respects they are completely identical with Spirifer cheehiel typ.

Spirifer (Hysterolites) bidevexus n. sp.

(Pl. V, fig. 52 a—b).

1. Spirifer Cheehiel: Stuckenberg (pars.). Mem. Acad. Sciences, SPB, XXXIV, S. 9, Taf. II, Fig. 1.

The shell is trapezoidal in outline, of strongly varying dimensions. The greatest width corresponds to the hinge margin. The ears are small, but sharply outlined. The ratio of width to length fluctuates around 1.7, i.e. in general it is less than in the typical Spirifer cheehiel (less than two).

The ventral valve is moderately convex, with a low, incurved beak. The area is well developed and usually has the appearance of a low triangle. The height of the area is, in general, the same as in the typical Spirifer cheehiel; rarely the area is lower, with nearly parallel margins. The sinus begins at the beak, is moderately developed, but is quite distinctly expressed. The bottom of the sinus is smoothly rounded, but sometimes in its anterior part (usually already within the tongue) a weak median swelling appears—as though an initial stage in the development of the median ridge characteristic of the species Hysterolites mesolobus Korovin; however, this swelling is very weakly expressed and never develops into a true rib. The tongue is moderately high, triangular in outline; its height is always somewhat less than the width of the sinus near the anterior margin; the latter is equal to the width of 3–5 adjacent ribs.

The dorsal valve is considerably more convex than the ventral valve and has a low area, as is characteristic of the typical Hysterolites cheehiel. The fold, extending from the very beak, is high and broad, roof-shaped, with a sharp crest; its sides are not curved surfaces, but planes meeting at an angle of about 80° near the anterior margin. The width of the fold near the anterior margin is equal to the width of 3–5 adjacent ribs.

The character of the sculpture is exactly the same as in Hysterolites cheehiel. On each side of the fold and sinus there are 6–7–8 folds.

Dimensions of several specimens:

width	72	54	80
length	42	31	47
thickness	29	22	35

Hysterolites bidevexus is quite clearly distinguished from Hysterolites cheehiel by the trapezoidal outline of the shell, by the smaller ratio of width to length (in adult specimens), and, chiefly, by the different character of the fold, which has been described in detail above. I consider the differences cited sufficient to separate the forms described into a distinct species, although it is connected by intermediate forms with Hysterolites cheehiel Kop.

In the Lebedyansk Devonian, Hysterolites bidevexus occurs together with Hysterolites cheehiel, but is a much less widespread form. Specimens of this species were obtained from the Kitata River, below the cattle trail, and from the Alchedat River, opposite the eastern end of the village of Lebedyanskoye.

Hysterolites bidevexus also occurs in the Minusinsk Basin (see synonymy) and in the Altai.

Spirifer (Hysterolites) mesolobus Korovin.

(Pl. V, figs. 48, 49, 50).

1. Spirifer Cheehiel Kon., n. var. mesoloba: Korovin. Essay on the geological structure and mineral resources of the Tomsk District, p. 35.

In the cited work by Prof. Korovin, among other forms of the Lebedyansk Devonian, it is listed (without description) as a variety of the species

Koninck’s form, characterized, as is evident from its name, by the presence of a median rib in the sinus. So substantial a distinction, it seems to me, may serve as sufficient grounds for separating this form as a special species of the subgenus Hysterolites.

The shell, as in Hysterolites cheehiel, is of strongly variable outlines and dimensions (up to 100 mm in width and 50 mm in length). The structure of the areas is also entirely analogous to that in Koninck’s species: a well-developed, indistinctly triangular, rather high (5–8 mm) area of the ventral valve, and a very low area of the dorsal valve with parallel margins, forming an acute dihedral angle. The sinus is normally developed; the saddle is well expressed, moderately high, rounded (in contrast to Hysterolites hidevexus). The sculpture is the same as in other representatives of the subgenus Hysterolites: in particular, in one specimen, within the sinus there is beautifully preserved the finest radial striation, which is far from often observable in less well-preserved specimens (Pl. V, fig. 48).

The distinctive feature of this species, as already noted above, is the presence in the sinus of a median ridge. The latter is not at all expressed in the beak-adjacent part of the sinus and appears at a distance from the beak of \(1/3\), and even \(1/2\), of the shell length. In the anterior part of the sinus it is a massive, broad ridge, on which there are several swellings at the places where it is crossed by the sharpest of the lamellar growth marks.

Hysterolites mesolobus occurs together with Hysterolites cheehiel, but belongs to rather rare forms. Specimens of this species have been found along the Alchedat River, near the cemetery; apparently, as a very rare form, Hysterolites mesolobus also occurs in the outcrops along the Kitat.

Spirifer (Hysterolites) semicostalis n. sp.

(Pl. V, figs. 51 a—b; 54).

In addition to the species Hysterolites mesolobus described above, in the Lebedyanskian Devonian there occurs another form that has a rib in the sinus of the ventral valve, but is not identical with the species mesolobus.

With respect to the outline of the shell, Hysterolites semicostalis is analogous to Hysterolites cheehiel typ.; the dimensions vary, apparently, within equally broad limits: the collection contains specimens of Hysterolites semicostalis of medium and large size. The areas of both valves are developed in the same way as in Hysterolites cheehiel; in young specimens the triangular outline of the area of the ventral valve is expressed rather distinctly, while in adult individuals the area is bounded by parallel margins. The saddle and sinus have the same character as in Hysterolites cheehiel. Likewise, the sculpture in the species being described shows no deviations from the usual type of sculpture of the subgenus Hysterolites.

The specific character of the form described is the presence of a thin median little rib running along the bottom of the sinus. This little rib begins at the very beak and can be traced to half the length of the shell, gradually weakening and finally disappearing entirely in the anterior part of the sinus. The little rib is rounded, very thin and weak, although quite distinct; its width does not exceed a millimeter, i.e., it is several times narrower than the folds on the lateral parts of the valves. The height of the little rib is very insignificant: in the profile of the sinus (the beak and umbonal part) it forms a very weak projection. The width of the little rib remains almost unchanged throughout its entire extent.

The distinction between Hysterolites mesolobus Korov. and Hysterolites semicostalis presents no difficulty. In the first species, in the sinus there lies a powerful, coarse—

a ridge, entirely inconspicuous in the umbonal and apical part of the sinus, but near the anterior margin reaching the width and height of the radial folds adjacent to the sinus. In Hysterolites semicostalis, a fine riblet runs along the bottom of the sinus, visible only in the apical and umbonal part of the sinus. In the case of very weak development of the median riblet, it is more difficult to distinguish Hysterolites semicostalis from Hysterolites cheehiel typ. (cf. Fig. 54 and Fig. 55 on Pl. V).

The dimensions of our specimens of this species:

length	width	thickness	height of the area of the ventral valve
~23	42	—	3
~30	52	~21	—
38	~80	33	6

Hysterolites semicostalis belongs to the rare forms of the Lebedyanskii Middle Devonian. Specimens of this species were found on the Alchedat River near the cemetery.

Spirifer (Hysterolites) mirus n. sp.

(Pl. VI, Fig. 57a–c).

One well-preserved specimen from our collection of Lebedyanskii spirifers, belonging to the subgenus Hysterolites, differs sharply from all forms of this subgenus by its peculiar habitus, abnormal for this group, which is due to the hypertrophied development of the sinus and saddle.

The shell is extended in width: the ears are broken off, but, apparently, the full width exceeds the length by a factor of three. The general outline of the shell gives, to some extent, a bilobed figure, because of the strong development of the sinus. Owing to the bending of the lateral margins, the ears are rather clearly outlined; they are broad in the part that has been preserved and, apparently, long.

The ventral valve is comparatively weakly convex. The greatest convexity falls on the umbonal part and the lateral parts lying between the broad sinus and the ears; between the convex lateral parts of the valve and the ears there is a distinct depression separating off the ears. The beak is moderately high, curved. The area is bounded by parallel margins; its height is 7 mm, i.e. the same as in Hysterolites cheehiel typ. The sinus begins from the very beak and quickly reaches considerable width and depth: the width of the sinus near the anterior margin equals half the preserved width of the shell or, approximately, one third of the full width (the width of the sinus corresponds to 7–8 adjacent ribs). But especially noteworthy among the elements of the sinus is the tongue: its height is almost equal to the length of the sinus from the beak to the frontal margin. The tongue has the outline of an isosceles triangle with an angle of 45° at the apex. At the intersection of the bottom of the sinus and the plane of symmetry of the shell, a full quarter of a circle is obtained, with a radius of about 4 cm (i.e. the curve running along the bottom of the sinus from the beak to the end of the tongue of the sinus has a length of 70 mm). The bottom of the sinus, smoothly rounded in the umbonal part, becomes

Fig. 4. Spirifer (Hysterolites) mirus n. sp.

flat near the anterior margin, while already within the tongue there gradually appears on it a swelling in the form of a broad, rounded, short rib (or fold), which, however, disappears again toward the top of the tongue.

The dorsal valve, weakly convex on the lateral parts, is sharply raised near the saddle. The saddle, distinctly expressed already at the very beak, is narrow, compressed from the sides, very high, with a blunted crest. Its width near the anterior margin is equal to the width of three adjacent ribs.

The sculpture is exactly the same as in Hysterolites cheehiel Kon. On each side of the saddle and sinus there are 7–8 folds.

Dimensions of the specimen: length 38¹); width ~90; thickness 39.

The distinguishing features of this species are the excessive development of the sinus and saddle, in particular—the exceptionally high tongue of the sinus, the great width of the latter, and also the height and lateral compression of the saddle.

The exact locality of the point at which the described specimen was found is unknown.

Spirifer (Hysterolites) orthogonalis n. sp.

(Table VI, fig. 58 a—c).

This is the only form among the Lebedyansk representatives of the subgenus Hysterolites possessing a hinge margin smaller than the greatest width of the shell.

Specimens are of medium size; the shell is developed in width: the ratio of width to length is ~1.6. The outline of the shell is subrectangular, because the lateral margins form angles of 90° with the hinge line. The greatest width of the shell corresponds to the middle of the length, or even lies closer to the anterior margin. Both valves are equally and considerably convex.

The area of the ventral valve is low or moderately high; the area of the dorsal valve is linear. The umbonal part of the dorsal valve is often raised above the hinge line, and the beak is curved; therefore the beak of the ventral valve lies upon the umbo of the dorsal one. In other cases the beaks simply touch.

The sinus begins at the beak, moderately broad, with a deep and rounded bottom. The tongue is arcuate, moderately high. The width of the sinus near the anterior margin is equal to the width of three to four adjacent ribs. The saddle is normally developed, smoothly rounded, less broad than the sinus; its width is equal to the width of 2–2.5 adjacent ribs.

The sculpture is of the same type as in the other representatives of the subgenus Hysterolites. But the radial folds are flatter and broader, less distinctly expressed than usual, especially on the ventral valves. The concentric growth marks and radial striation are the same as in the other species of Hysterolites.

Dimensions:

length	width	height	length of hinge margin
28	41.5	25.5	37
21	34	16.5	33

From all the other Lebedyansk representatives of the group Spirifer cheehiel, the described species differs above all in its straight cardinal angles and comparatively short hinge margin, as well as in the greater convexity of the valves and the character of the convexity: the swollen surface of the val—

¹) The greatest measurement in length—from the umbo to the end of the tongue of the sinus—48 mm.

Classification table of representatives of the subgenus Hysterolites in the Lebedyan Middle Devonian

Name of form	Outline of shell	Ratio of width to length in adult individuals	Area of the ventral and dorsal valves	Saddle	Sinus	Most important differences from Hysterolites cheehiel typ.
Hysterolites cheehiel Kon.	Subtriangular, more rarely trapezoidal or semielliptical.	2–2.5, rarely less than 2.	Area of the ventral valve 5 times higher than the area of the dorsal valve.	Normally high, rounded	Normally developed, rounded, smooth	—
Hysterolites cheehiel Kon., var. alata Stuck.	Subtriangular	About 3.	Same	Same	Same.	Ratio of width to length
Hysterolites bidevexus n. sp.	Trapezoidal.	Less than 2 (about 1.7)	Same	Sharp-crested, roof-shaped	Same	Ratio of width to length, outline of the shell, character of the saddle.
Hysterolites mesolobus Konin.	As in H. cheehiel	As in H. cheehiel.	Same	As in H. cheehiel.	Thick ridge in the anterior part of the sinus.	Thick ridge in the sinus
Hysterolites semisolutus n. sp.	Same	Same	Same	Same	Thin rib in the apical and umbonal part of the sinus.	Thin rib in the sinus
Hysterolites minutus n. sp.	Bilobate in character.	2–3	Same	Very high, narrow (compressed from the sides).	Very broad, with a hypertrophically developed tongue.	Hypertrophied development of the saddle and sinus.
Hysterolites orthogonalis n. sp.	Subrectangular.	About 1.6	Area of the ventral valve only slightly higher than the area of the dorsal valve.	As in H. cheehiel.	As in H. cheehiel.	Short hinge margin, straight cardinal angles.

...the umbo (especially of the ventral valve) descends steeply toward the margins of the shell, particularly steeply toward the anterior margin; in the other representatives of the subgenus Hysterolites, however, the ventral valve is much less convex, and the lowering of its surface toward the frontal margin is gentler and more gradual.

Hysterolites orthogonalis belongs among the rare forms in the Lebedyanskii Middle Devonian. A few specimens of this species were found along the Alchedat River near the cemetery.

Spirifer (Delthyris) altschedatiensis Korovin

(Pl. VI, figs. 59 a–b, 60, 61; Pl. VII, figs. 65 a–c).

1. Spirifer Altschedati. Korovin. Geological essay, etc., p. 37.

Shells of medium and large size. The hinge margin is long and straight; it is somewhat less than the greatest width of the shell. The cardinal angles and lateral margins are rounded; the anterior margin is somewhat straightened (it forms a very shallow arc). The shell is moderately developed in width.

The ventral valve is strongly convex, with a curved beak. The area is high, triangular, concave; it is not sharply delimited from the lateral parts of the valve. The height of the area increases with the growth of the shell; the ratio of the height to the length of the base of the area varies from \(1/3\) to \(1/4\). On the area there is fine horizontal and vertical striation. The delthyrium is large, open; its width varies greatly. The sinus begins at the very beak and attains considerable width near the anterior margin; the depth of the sinus is moderate, the floor smoothly rounded. The tongue is high, arcuate. The sinus is bounded by two rounded, broad folds.

The dorsal valve is semicircular in outline, less convex than the ventral valve. The area of the dorsal valve is very low, triangular; its height is 2–3 mm. The fold begins at the beak, is high, with a broadly rounded top.

The sculpture consists of a few rounded radial folds, separated by broad, likewise rounded interspaces. The number of folds on the dorsal valve is 4 or 6, 2–3 on each side of the fold; only two pairs of folds are clearly expressed, the third pair (if present) is only indicated. Sometimes on each side of the fold there is only one distinct fold. On the ventral valve there are likewise 4 folds, not counting the two that bound the sinus; only in the largest specimen is one additional pair of folds very weakly indicated. Where the outer layer of the shell is preserved, dense concentric lamellar growth marks are clearly visible, entirely analogous to those in the group Spirifer cheehiel Kon. There is also the finest radial ribbing, characteristic of the subgenus Delthyris Dalm. At the margins of the shell the lamellar character of the growth marks is very sharply expressed (see fig. 59 d on Pl. VI).

Inside the ventral valve there is a long and high septum and well-developed dental plates.

Dimensions:

length	width	thickness	height of area of ventral valve	width of sinus
49	52	37	15	19
38	41	27	12	18
29	35	24	6	14
25	34	21	8	13

Delthyris altschedatiensis shows the greatest similarity to folded specimens of Delthyris macrorhyncha Schnur (see 60, p. 57, Taf. V, fig. 10), from which it differs by more sharply expressed radial...

folds and the absence of a longitudinal depression on the saddle¹. Among American forms, Delthyris raricosta Conr. shows a known similarity to the present species.

D. altschedatiensis occurs rather frequently along the Kamenushka River (near its mouth) and along the Alchedat River by the cemetery; as a very rare form it is also known farther up the Alchedat. It has not been found in the outcrops along the Kitat.

Spirifer (Delthyris) robustus Barrande.

(Table VII, figs. 67 a—b).

1. Spirifer robustus: Scupin. Spirif. Deutschl., S. 55, Taf. V, Fig. 4 (Synon. ib.).
   non! Spirifer robustus: Webster. 1906; non! Sp. robustus: C. L. Fenton and M. A. Fenton 1924.

The outlines of the shell are the same as in Delthyris altschedatiens, but the hinge margin is half as short as the greatest width of the shell. Both valves are equally convex.

The area of the ventral valve is moderately developed, triangular, not sharply delimited; its height amounts to 1/3 of the length of its base. The beak is incurved. Almost from the very beak begins the sinus, representing a narrow, rather deep depression with a rounded bottom. The sinus is distinctly bounded. The tongue of the sinus is arcuate, with a somewhat straightened top. Inside the ventral valve there is a well-developed spondylium.

The dorsal valve apparently has a very low area. The saddle is not noticeable in the umbonal part; throughout the rest of its extent it is a moderately developed elevation with a flatly rounded top. On the anterior half of the valve it is separated from the lateral parts by indistinct, broad depressions.

Radial folds are absent on the surface of the shell. The outer layer of the shell has not been preserved, but in places traces of concentric growth marks and radial striation are quite clearly visible, entirely analogous to those in Delthyris altschedatiensis.

The Lebedyansk specimens of Delthyris robusta are closest to the Bohemian representatives of this species from stage F, figured by Barrande (3, pl. V, fig. 1—4); the only difference is that in the Bohemian specimens the saddle can be traced to the beak. Nalivkin (43, 114) distinguishes as a separate variety mesodevonica the Middle Devonian representatives of D. robusta. This variety differs from the typical (Lower Devonian) form by a less developed saddle and sinus and by a higher area. However, in the degree of development of the saddle, sinus, and area, the Lebedyansk specimens stand closer to the Lower Devonian D. robusta than to those figured by Nalivkin.

In our collection there are only three specimens of Delthyris robusta, obtained from the Alchedat River.

Spirifer (Delthyris?) mesocostalis Hall.

(Table VII, figs. 68 a—b).

1. Spirifer mesacostalis: Hall. Pal. N. Y., vol. IV, p. 240, pl. XL, figs. 1—15.
2. Spirifer mesacostalis: Hall & Clarke. Pal. N. Y., vol. VIII, pt. II, pl. XXXIV, figs. 32—34.
3. Delthyris mesocostalis: Schuchert. Synopsis Amer. Foss. Brach., p. 207.
4. Spirifer (Delthyris) mesocostalis: Clarke & Swartz. Maryland Geol. Surv. Upper Devonian, p. 601, pl. LVIII, figs. 11—23; pl. LIX, figs. 1-2.
5. Delthyris mesocostalis: Khafin. Nizhnefransk. brakh. okrain Kuzbassa, p. 14, pl. II, figs. 32—35.

In the cited work I gave a description of Siberian representatives of D. mesocostalis, originating from the Lower Eifelian deposits of Kuzbass. The Lebedyanskoye specimens of this species show no differences; only some of them reveal a somewhat greater convexity of the ventral valve and a greater curvature of the beak.

It should be noted that, despite the complete identity of all external characters of the Lebedyanskoye D. mesocostalis with the American representatives of this species (and with the Lower Eifelian Kuzbass representatives), I had no opportunity, in the Lebedyanskoye material, to observe a septum in the ventral valve, which (the septum) in this species is in general very weakly developed¹.

D. mesocostalis is externally very close to Spirifer bouchardi Murch., var. ales mihi from the Lower Eifelian deposits of Siberia, differing from this form by the higher area of the ventral valve, which has a triangular outline. The isolated dorsal valves of these two forms are indistinguishable.

In the Lebedyanskoye Devonian, D. mesocostalis occurs together with Spirifer cabedanus Vern. et Arch., apparently characterizing the highest horizons of the Middle Devonian.

Spirifer (Eoreticularia) aviceps Kayser.

1. Spirifer aviceps: Kayser. Brach. Eifel, p. 578, pl. XI, fig. 4.
2. Reticularia aviceps: Gurich. Pal. Poln. Mittelg., p. 257, pl. IX, fig. 7.
3. Spirifer aviceps: Scupin. Spirifer. Deutsch., p. 41, pl. III, figs. 12–13.
4. Reticularia aviceps: Sobolev. Profile Gregorz. Vlozhy, p. 72.
5. Spirifer (Reticularia) aviceps: Reed. Dev. Fauna North Shan States, p. 105, pl. XVI, figs. 1–3.
6. Spirifer aviceps: Sobolev. Kielce-Sandomierz Range, p. 474.

One damaged specimen of this species is present in our collection. Like the typical German representatives of S. aviceps, our specimen has rounded shell outlines, a long, slightly curved beak of the ventral valve, a sharply delimited area, and very weakly expressed saddle and sinus.

Specimens from the Middle Devonian of Burma, referred by Reed (see the synonymy) to this species, differ in having a sharply expressed saddle and sinus and probably represent a certain local form of Kayser’s species.

The relationship of S. aviceps to related forms (Spirifer curvatus Schl., Spirifer maureri Holz., etc.) has repeatedly been discussed in the literature; our insufficient material (one damaged specimen) does not permit us to add any new data on this question.

Cyrtina heteroclita Defr.

(Pl. VI, figs. 64 a–b.)

Cyrtina heteroclita, which has a universal distribution within the Old World, belongs to the rare forms in the Lebedyanskoye Devonian: we have only one specimen of this species. Its Siberian representatives have been described more than once. Our specimen is a small shell of pyramidal habit. The area is high, triangular; the beak slightly curved. The saddle is broad, flat, without any signs of a longitudinal depression. The number of folds is 2 on each side of the saddle and sinus.

Dimensions: length — 11; width — 11.5.

The relationship of C. heteroclita to closely related forms is discussed in the monographs of Whidborne (75, III) and Nalivkin (43, 137).

In Kuzbass, Cyrtina heteroclita is common in the Middle and Upper Devonian.

Cyrtina heteroclita Defr., var. multiplicata Dav.

1. Cyrtina heteroclita Defr., var. multiplicata: Nalivkin. Brach. Upper and Middle Devonian of Turkestan, p. 138 (Syn. ibidem).

There is likewise only one specimen, exceeding the preceding one in size:

length	width
12	16	(ears broken off).

The area of the ventral valve is straight, slightly curved. The beak is not bent. On the area there is distinct horizontal striation. The delthyrium is narrow: its width amounts to 0.2 of the length of the base of the area. The sinus is moderately deep, with a rounded bottom; the width of the sinus is equal to the width of 5 adjacent ribs.

The dorsal valve is almost flat. The fold is low, bounded by shallow depressions. On the crest of the fold, toward the beak, a very weak depression is visible. On each side of the fold and sinus there are about 10 rounded radial ribs.

The presence of a weak depression on the fold brings our specimen close to Cyrtina Demarli Bouch. and Cyrtina varia Clarke (which apparently are synonyms), but in our specimen this depression is developed much more weakly (not visible without a lens).

C. heteroclita multiplicata is common in the Givetian deposits of Western Europe and Fergana.

Cyrtina heteroclita Defr., var. intermedia Oehlert.

(Pl. VI, figs. 62 a—b, 63; Pl. VII, fig. 66).

1. Cyrtina heteroclita, var. intermedia: Oehlert. Annales des Sci. Géol., vol. XIX, p. 42, pl. III, figs. 29–35.
2. Cyrtina heteroclita, var. intermedia: Dahmer, Jahrb. kön. pr. geol. L.-A. S. 228.

This form is considerably more widespread in the Lebedyanskii Devonian than the two preceding ones.

The shells are small, with a long hinge margin forming pointed extremities, which are rarely preserved. The area of the ventral valve is perfectly straight, rarely slightly concave near the beak. The difference from the preceding form consists in the smaller number of ribs—in our specimens 6, rarely 7, on each side of the fold and sinus.

With respect to the character of the fold, variations are observed: from sharply elevated, with steep sides, to almost flat. The sinus varies correspondingly.

Dimensions:

length	width	height of area
17.5	16	10
~11	14	~7—8
9	9.5	7

In Western Europe the variety intermedia occurs in the upper part of the Lower and the lower part of the Middle Devonian.

A considerable number of specimens of this variety was obtained from outcrops on the right bank of the River Kitat, north of the village of Lebedyanskoye.

Merista plebeia Sow.

(Table VII, figs. 70 a–c).

1. Atrypa plebeia: Sowerby. Géol. Transact. 2 Ser., v. V, p. LVI, figs. 12—13.
2. Terebratula scalprum: Roemer. Das Rheinisch. Übergangsgeb., S. 68, Taf. V, Fig. 1.
3. Terebratula prunulum (pars): Schnur. Brach. Eifel., S. 190, Táf. XLIV, Fig. 1 a—c.
4. Merista plebeia (pars): Davidson. Brit. Dev. Brach., p. 20, pl. III, f. 2—6.
5. Merista plebeia (pars): Kayser. Brach. Eifel, S. 551.
6. Merista plebeia: Chernyshev. Materials for the Study of the Devonian Deposits of Russia, p. 9, pl. 1, fig. 19.
7. Merista plebeia: Oehlert. Ann. Sciences, géol., p. 25, pl. II, fig. 25—27.
8. Merista plebeia: Whidborne. Dev. Fauna South. Engl., p. 98, pl. XII, figs. 3—6.
9. Dicamara scalprum: Hall and Clarke. Pal. N.—Y., vol. VIII, pt. II, p. 73, pl. XLII, figs. 13—16.
10. Merista plebeia: Holzapfel. Obere Mitteldevon, S. 244.
11. Merista plebeia: Gürich. Palaeoz. im Poln. Mittelgeb., S. 268.
12. Merista plebeia: Drevermann. Fauna oberdev. Tuffbreccie, S. 173.
13. Merista plebeia: Petz. Materials for the Knowledge of the Devonian Fauna of the Kuznetsk Basin District, p. 127.
14. Merista plebeia: Sobolev. Devonian Deposits of Prof. Gregorzh. et al., p. 81.
15. Merista plebeia: Reed. Dev. Faun. North Shan States, p. 113, pl. XVI, figs. 23 a—c.
16. Merista plebeia: Sobolev. Middle Devonian of the Kel’-Sand Range, p. 486.

This species belongs to the rare forms in the Lebedyanskaya fauna. The shell is of small size, elongate-oval, with an indistinctly pentagonal outline, and with moderately and equally convex valves. The beak of the ventral valve is curved, but not pressed against the umbo of the dorsal valve. A pseudoarea (false area) is distinctly expressed. The sinus is a very weak depression, noticeable only near the very anterior margin. The tongue is very low, gently arcuate. The saddle of the dorsal valve is somewhat more clearly expressed near the frontal margin.

Dimensions:

width — d	length — l	d/l	thickness — c	d/c
11.5	14	0.82	9	1.28
9	9.5	0.95	6	1.50

Representatives of the species M. plebeia show considerable variability with respect to size, shell outline, and the character of the profile. In all these respects our specimens are quite similar to the Middle Devonian Merista plebeia from Burma, figures of which were given by Reed (see the synonymy).

The relations of M. plebeia to the closely related forms M. lacryma Sow., Merista prunulum Schn., and Merista Herculea Barr. have repeatedly been considered in the literature. Some authors (Davidson, Kayser) understand the species M. plebeia broadly, usually including M. lacryma and M. prunulum in it. The differences between M. plebeia and M. lacryma are considerable and were formulated with the greatest precision by Reed (op. cit.). M. prunulum of Schnur should be regarded as a collective term encompassing various forms, among which, in any case, both M. plebeia and M. lacryma occur (see the synonymy of these two species).

The Merista plebeia described by Chernyshev from the Koltuban Upper Devonian differs from typical representatives of this species in the weak development of the shell in width and in this respect approaches M. lacryma (as Holzapfel also regards it—op. cit., S. 244). However, M. lacryma possesses a considerably more inflated shell.

The complicated synonymy of M. plebeia and the details of the relations of this species to closely related forms have been analyzed with exhaustive completeness in Reed’s monograph (op. cit., p. 114).

M. plebeia is widely distributed in the Middle Devonian of Europe and Asia and is encountered rarely in the lower part of the Upper Devonian. In the Kuzbass, Pets brings this species from \(D_2^2\) of the western margin of the Kuznetsk Basin.

One specimen was delivered from the Kamenushka key, another—from the northern outcrops of the Lebedyanskoye Devonian on the Kitat River.

Merista lacryma Sow.

(Table VII, figs. 71 a–c)

1. Atrypa lacryma: Sowerby. Geol. Transact. 2 Ser., Vol. V, pl. LVI, fig. 9.
2. Terebratula prunulum (pars): Schnur. Brach. Eifel, S. 190, Taf. XXVII, Fig. 1 a, b. c.
3. Merista plebeia (pars): Davidson. Dev. Brach., p. 20, pl. III, figs. 7—10.
4. Merista plebeia: Venyukov. Sediments of the Devonian System of Mugodzhar, p. 143, pl. II, fig. 7.
5. Merista lacryma: Holzapfel. Obere Mitteldevon, S. 245, Taf. XVII, Fig. 4, 5.
6. Merista lacryma: Drevermann. Fauna oberdev. Tuffbreccie, 173.
7. Merista lacryma: Pets. Materials toward the knowledge of the fauna of the Devonian deposits of the environs of the Kuznetsk Basin, p. 128.
8. Meristella aff. lacryma: Reed. Dev. Faunas North Shan States, p. 118, pl. XVI, figs. 30 a, b.

A small, strongly swollen shell of elongate-oval outline. The anterior margin is straight. The greatest width of the shell is at the middle.

The ventral valve is strongly and regularly convex, with the beak bent toward the umbo of the dorsal valve. There is no pseudoarea. The sinus on the anterior part of the valve is clearly expressed. The tongue is rather high, arcuate. The dorsal valve is spherically swollen. The saddle near the anterior margin is indicated by two weak depressions bounding it, forming small bends of the frontal margin on the sides of the tongue of the sinus. There are no depressions on the saddle.

The outer surface of the valves is covered with dense, fine concentric lines.

Dimensions:

length—l	width—d	d/l	thickness—c	d/c
10.5	10	0.95	8.2	1.22

Our specimens of M. lacryma show the greatest similarity with the English representatives of this species figured by Davidson. The German specimens of M. lacryma figured by Holzapfel differ somewhat in the outline of the shell. The form cited by Venyukov from the Stringocephalus beds of Mugodzhar under the name M. plebeia, in outline of the shell and in its inflation, stands closer to M. lacryma, but has a longer beak.

M. lacryma has the same distribution as M. plebeia. In the Lebedyanskoye Devonian they occur together, both being rare forms.

Meristella nasuta Conr.

(Table VII, figs. 73a-c).

1. Meristella nasuta: Hall. Pal. N. Y., vol. IV, p. 299, pl. XLVIII, figs. 1—25.
2. Meristella nasuta: Schuchert. Syn. of Amer. Foss. Brach., p. 268 (synonymy Ib.).
3. Meristella nasuta: Kindle. Onondaga Fauna, p. 85, pl. VII, fig. 7.
4. Meristella (Whitfieldia) nasuta: Walcott. Palaeont. Eureka Distr., p. 48, pl. III, fig. 8.

There are two specimens of this species in the collection.

The shell is of medium size, developed in length. The outlines of the shell represent an almost regular ellipse with two axes of symmetry.

Dimensions: length 20.5, 18; width 19, 15; thickness 13, 10.

The ventral valve is moderately convex; the greatest convexity is slightly above the middle of the shell. The beak is steeply bent and pressed against the umbo of the pro—

opposite valve. The pseudoarea is not developed. There is no distinct sinus; only on the anterior part of the shell is there a broad, very shallow depression, forming a rather high tongue with a flatly rounded top.

The dorsal valve is considerably less convex than the ventral. There is no saddle: only the anterior end of the valve is raised by the tongue of the ventral valve, which gives the shell a profile typical of meristellids.

The surface of the valves is smooth, with a few very weak signs of shell growth.

The specimen described above is quite similar to young Middle Devonian representatives of this species from the State of New York, described by Hall; larger (adult) individuals differ from our specimen in the rounded-rhomboidal outline of the shell. The form described by Walcott from the Lower Devonian of Nevada under the name M. (W.) nasuta differs from this species in the greater convexity of the dorsal valve, a distinct sinus on the ventral valve, and a longitudinal depression on the dorsal valves, and, as this author justly notes, stands closer to M. tumida Dalm. than to M. nasuta. Judging from the description and figures given by Kindle, the Pennsylvanian Middle Devonian representatives of M. nasuta are fully analogous to the New York ones.

In external characters the young individuals of Merista herculea Barr. are rather close to our specimen (see, for example, 3, pl. 134, VIII), differing in a more developed sinus, greater convexity of the dorsal valve, and usually in the beak of the ventral valve not being pressed against the umbo of the dorsal valve.

Our specimens come from the Alchedat River, near the cemetery.

Meristella yanischewskii n. sp.

(Pl. VII, figs. 72 a–c).

The shell is of considerable size, strongly inequivalved, with the ratio of width to length close to unity. The greatest width lies nearer the anterior margin, owing to which the outline of the shell appears as an irregular pentagon: the two sides of the latter adjacent to the beak are almost twice as long as the sides next to them.

The ventral valve is strongly convex. The beak is strongly incurved: the curve of the valve profile, approaching the beak, becomes horizontal and then bends downward. The beak lies on the umbo of the dorsal valve. The sinus is developed only on the anterior part of the valve, representing, close to the anterior margin, a shallow but broad depression with steep sides and a flat bottom. The sinus ends in a rather high tongue.

The dorsal valve is considerably smaller than the ventral and less convex. Its beak is hidden beneath the beak of the ventral valve. The saddle is completely absent in the apical and umbonal part of the valve, but is quite distinctly expressed near the anterior margin, where the surface of the valve is raised by the tongue of the sinus of the ventral valve.

The outer surface of the valves is covered with numerous growth lines.

Dimensions: width—25.5; length—26.5; thickness 17.5.

Our species has some similarity to Meristella barrisi Hall from deposits of the Hamilton group of North America, differing from Hall’s species in lesser development in length, a higher umbo, a more incurved beak, and a more sharply expressed saddle near the anterior margin. Apparently very close is M. kütsingensis Grabau from the Chinese Middle Devonian (19, 193, fig. 131).

The single specimen of this species was found together with M. nasuta.

Athyris subacuminata n. sp.

(Pl. VII, figs. 74, 75, 76 a—b, 77).

The shell is small or of medium size, inflated, transversely elongated, with a sharply expressed fold and sinus. The outline of the shell is sub-rhombic. The sinus of the ventral valve begins at the very apex, or almost at the very apex, and, in typical forms, is a rather narrow but deep depression with fairly steep sides and a rounded bottom. The sinus is bounded by distinct rounded folds. The tongue of the sinus is high, arcuate. The width of the sinus near the anterior margin is approximately \(2/5\)—\(1/2\) of the width of the shell. Corresponding to the strong development of the sinus, the fold in our species is also sharply expressed, although it begins at some distance from the apex. On the anterior half of the shell the fold is very high, narrow, but not sharp, bounded by deep depressions. In large specimens the fold and sinus are more strongly developed than in small ones.

The growth marks consist of coarse, very sharp lamellae; in the apical region they are usually few in number.

Dimensions:

	length	width	thickness
	19	24	14
	12.5	15	9
	7	7.5	4

Closest to our species in general character is the Upper Devonian A. acuminata Drev. (15, 170), which differs in its acute-angular fold and sinus and weak growth marks. A more distant resemblance to A. subacuminata is shown by A. undata Defr. (see, e.g., 5, pl. VII, fig. 1). Sobolev (62, 485) indicates the presence in the Polish Middle Devonian of a form close to Defrance’s species, but does not describe it.

In the Lebedyansky Devonian, A. subacuminata has the widest distribution among the other athyrids. Specimens of this species were found in large numbers along the Kitat River, in the northern outcrops of the Lebedyansky Devonian.

Athyris concentrica Buch.

(Pl. VIII, fig. 82 a—b).

1. Athyris concentrica; Khalfin. Lower Frasnian brachiopods of the margins of Kuzbass, p. 16, pl. III, figs. 38—42.

To this species I assign weakly and moderately convex shells of rounded-pentagonal outline, with the fold and sinus developed only near the anterior margin, and with fine, dense, concentric growth marks. A. concentrica is common in the Lower Frasnian deposits of Western Siberia, and the Lebedyansky representatives of this species do not differ in any way from the Lower Frasnian ones described and figured in the work cited in the synonymy. The convexity of the shell and the degree of development of the fold and sinus vary considerably. Usually the sinus and fold are quite distinctly expressed (although they do not attain great development). With very weak development of the fold and sinus, A. concentrica is difficult to distinguish from the close A. fultonensis Swallow (see below). Specimens of A. concentrica possessing a flat fold with a weak depression on it are very close to A. vittata Hall.

Dimensions:

	length	width	thickness
	22	25	—
	14.5	17	7.5
	8	8.5	7

Specimens of A. concentrica in the Lebedyan Devonian are not as numerous as A. subacuminata, but A. concentrica occurs at a larger number of localities (on the Alchedat and Kitagu rivers).

Athyris fultonensis Swallow.

(Table VIII, figs. 86 a—b).

1. Athyris fultonensis: Branson, Devonian of Missouri, p. 109, pl. XVII, figs. 1—4. (Synonymy ib.).

The Lebedyan specimens assigned by me to this species are as follows: the shell is small, moderately convex, slightly developed in width. The outline of the shell is rounded-pentagonal; the anterior margin is straightened. The ventral valve is moderately and regularly convex; its greatest convexity is somewhat above the middle (closer to the beak). The beak is short, curved, with a small round foramen at the end. The apical angle is about 120°. The sinus is entirely absent or only slightly expressed; accordingly, the line of junction of the valves, when the shell is viewed from the frontal margin, appears either completely calm or forms an insignificant bend toward the dorsal valve. The saddle is entirely absent. The outer surface is covered with dense, fine, concentric growth marks.

Dimensions:

length	width	thickness
11	12	7
11.5	12	6.5
11	12	6.5

A. fultonensis, according to Branson, in North America (Missouri) occurs in the Callaway limestone (a horizon transitional between \(D_2\) and \(D_3\)) and in the Snyder Creek shale (\(D_3\)); moreover, there are substantial differences between representatives of this species from one and the other horizon. Specimens from the Snyder Creek shale have a shell of longitudinal-elliptical outline, with length exceeding width (6, pl. XVII, figs. 1—3). Specimens from the Callaway ls. (ib., fig. 4) possess a shell of rounded-pentagonal outline, with predominant development in width¹. These specimens correspond more closely to Swallow’s diagnosis of A. fultonensis (6, 109), and, possibly, the specimens from the Snyder Creek sh. should be regarded as a distinct species.

The Lebedyan specimens are fully analogous to the specimens from the Callaway ls. The species closest to A. fultonensis is Athyris glassi Dav. (see the description), distinguished by its greater development in width and broadly rounded anterior margin. On the relationship between A. fultonensis and A. vittata, see Branson (6, 110).

In the Lebedyan Devonian, A. fultonensis occurs together with A. concentrica, in a somewhat smaller quantity than the latter.

Athyris rugata Davidson.

(Table VIII, figs. 84, 85).

1882–84. Athyris rugata: Davidson, Suppl. Dev. Brach., p. 26, pl. I, figs. 25, 25a.
1892. Athyris rugata: Whidborne, Dev. Fauna South Engl., p. 101.

Two specimens among our athyrids belong to this species. The shell is small, moderately convex, slightly developed in width. The outline of the shell is rounded. The ventral valve has a small, slightly curved beak. The sinus is very weakly developed and pres—

exists only as a slight depression on the anterior part of the shell. Likewise, the flat saddle is weakly expressed, noticeable only near the anterior margin of the dorsal valve.

The surface of the valves is covered with not very numerous, coarse growth marks, having the character of broad plates with sharp, sometimes uneven margins. This character of the growth marks distinguishes A. rugata from A. concentrica, which is close to it in the general form of the shell.

Dimensions:

length	width	thickness
9	10	5.5
10	10	6

A. rugata occurs in the Middle Devonian of England. In Lebedyanka it was found in the northern outcrops of Devonian rocks, along the Kitat River.

Athyris glassi Davidson.

(Pl. VII, fig. 79)

1882-84. Athyris glassi: Davidson. Suppl. Dev. Brach., p. 24, pl. 1, figs. 21--22.
1892. Athyris glassi: Whidborne. Dev. Fauna South. Engl., p. 100.
1930. Athyris glassi: Nalivkin. Semiluk and Voronezh beds, p. 78.

Like the preceding species, A. glassi is very rare in the Lebedyanka Devonian. A small, weakly convex shell of transversely elliptical outline. The ratio of width to length is 1.3. Both valves are regular and moderately convex, without sinus and saddle. The beak of the ventral valve is small, slightly curved. The apical angle is about 120°. Dimensions of the specimen: width--12; length--9.2; thickness--55. The external surface is preserved only in places; where it is preserved, it is smooth.

This species differs from A. concentrica in the absence of a saddle and sinus and in the transversely elliptical outlines of the shell. Especially characteristic in A. glassi is the broadly rounded frontal margin and the smooth transition of the anterior margin into the lateral margins, by which this species also differs from the closest A. fultonensis Swallow; the shell of the latter is less developed in width and has distinctly subpentagonal outlines.

A. glassi occurs in \(D_2\) of England. As a very rare form, Nalivkin cites it from the Semiluk beds of the Orel-Voronezh Devonian. In Lebedyanka A. glassi occurs as single specimens in the northern outcrops on the right bank of the Kitat River.

Athyris polita Hall.

(Pl. VIII, fig. 83a--c)

1. Athyris polita: Hall, Pal. N. Y., vol. IV, p. 293, pl. XLVII, figs. 31--33.
2. Athyris polita: Hall and Clarke, Pal. N. Y., vol. VIII, pt. II, pl. XLVI, figs. 1--5.
3. Athyris polita: Schuchert. Synopsis Amer. Foss. Brach., p. 149.

The shell is moderately convex, slightly developed in length, of elliptical outline. The anterior margin is straightened; the apical angle is about 100°. The greatest width is at the middle. The ventral valve is more convex than the dorsal; the greatest convexity is above the middle. The sinus begins at a distance of one third of the shell length from the beak; it is not deep and not sharply bounded, but on the anterior half of the valves it is quite distinct. The tongue is low, arcuate. The saddle is low, broad, bounded by weak depressions; it is expressed only on the anterior part of the dorsal valve. The external surface of the valves is covered with numerous, dense growth marks.

Dimensions:

length	width	thickness
14.5	13.2	8.5

Our specimen is quite similar to the American ones (compare, e.g., 23, pl. XLVII, figs. 23–26), having only a somewhat less inflated shell. In North America (New York) A. polita occurs in the Upper Devonian (Chemung group).

Our specimen of this species comes from the Alchedat River, above the village of Lebedyanskoye.

Athyris gracilis Sandb.

(Table VII, figs. 80 a–c).

1. Spirigera gracilis: G. und Fr. Sandberger. Verst. d. rhein. Schicht. Nassau, S. 329, Taf. XXXII, Fig. 12, 12a, 12b.

2. Terebratula concentrica, var. γ. Schnur. Brach. Eifel, S. 192, Taf. XLIV, figs. 10a-b, (non. Taf. XXVII, fig. 3a–c).

3. Athyris concentrica, var. gracilis: Kayser. Brach. Eifel, S. 548.

The shell is small, strongly inflated, somewhat more developed in length than in width. The outline of the shell is rounded-pentagonal; the greatest width is in the middle. The ventral valve is more convex than the dorsal one, with a broad, strongly curved beak. The apical angle is about 80°. From the very beak to the anterior margin there passes a shallow but distinct sinus, bounded by weakly developed folds. The tongue is low, arcuate. The saddle on the dorsal valve is not developed at all, and only near the very anterior margin is it faintly indicated by barely perceptible depressions on its sides. The outer layer of the shell has not been preserved, and therefore the sculpture is not visible.

Dimensions of the single specimen: width—11, length—12.5, thickness—8.5.

Closest to this specimen is Spirigera gracilis Sandb., distinguished by a somewhat more sharply expressed pentagonal outline of the shell and by a somewhat sharper sinus and the folds bounding it. Kayser, who revised the material concerning the brachiopods of the Eifel, pointed to the identity of A. gracilis with Terebratula concentrica, var. γ of Schnur, although the figures of these forms given in the old monographs of Schnur and the Sandbergers (see synonymy) reveal appreciable differences. Our specimen fully agrees with the brief description of A. gracilis given by Kayser.

A. gracilis occurs in the Stringocephalus deposits of Germany.

Athyris circularis n. sp.

(Table VIII, figs. 87a—b).

The shell is isometric, from small to medium in size. The outline of the shell is circular, at times indistinctly pentagonal. The shell is moderately inflated in small specimens and strongly inflated in large ones. The greatest width of the shell is at the middle distance between the beak and the frontal margin. The valves are equally convex. The beak of the ventral valve is moderately long, curved. The sinus is developed extremely weakly: even in the largest specimens it represents a completely flat depression near the very anterior margin. Often the sinus is perceptible only in the bend of the frontal margin, which forms a low, flatly arcuate tongue. In the smallest specimens the sinus is completely absent. The dorsal valve has a regularly and uniformly convex surface, without any indication of a saddle even in the largest specimens. The outer surface of the shell is covered with dense, regular growth marks, characteristic of the genus Athyris M’Coy.

In the collection described, for A. circularis it is possible to select a complete growth series, the extreme members of which have the following dimensions:

length — l	width — d	d/l	thickness — c	d/c
19.5	19.5	1	11	1.8
6.5	6.5	1	4	1.6

A. circularis belongs to those forms which, while not amenable to identification with other species, also do not possess sharply specific features that would permit them to be separated at once. Characteristic of A. circularis is the combination of the following features: rounded outlines and great inflation of the shell, very weak development of the sinus and absence of a saddle. The closest form is A. fultonensis Swall., distinguished by a considerably lesser convexity of the shell. A. glassi Dav. has a shell likewise less convex, more developed in width and with different outlines (see description). A. globularis Phill., close in the general form of the shell to large specimens of our species, differs in having a saddle (although a low one) and a greater development of the sinus.

A. circularis, together with A. subacuminata and A. concentrica, is the most widely distributed among the athyrids of the Lebedyan Devonian. Specimens of A. circularis have been obtained from the northern outcrops along the Kitat River,

Athyris cf. triplezioides Oehl.

Two small, moderately convex shells. Outlines subrhombic; the ratio of width to length is close to unity. The apex of the ventral valve is high, curved. The sinus begins at the very apex, is deep, sharply delimited, narrow. A long, drawn-out tongue is characteristic. The saddle in the umbonal part is not expressed at all, but on the anterior half of the dorsal valve it is high, clearly bounded by depressions. The surface of the shell is covered with dense, regular growth marks.

Dimensions:

	length	width	thickness
	10.5	10.5	6.5
	12	12	8

Closest is A. triplezioides Oehlert (5, p. 112, pl. VII) from the Lower Devonian of France, differing in its larger size and in the fact that the sinus begins at a considerable distance from the apex. Apparently, our specimens represent a new species. They come from the outcrops along the Kitat River,

Athyris trapezoidalis Peetz.

(Table VII, figs. 78a—c).

1. Anathyris trapezoidalis: Peetz. Materials for the knowledge of the fauna of the Devonian deposits of Kuzbass, p. 111, pl. V, figs. 4a—c.

Shell of medium size, considerably inflated, isometric. The outline of the shell is a regular pentagon; apical angle about 110°. The valves are equally convex. The apex of the ventral valve is low, sharp, slightly curved. From the very apex there runs a sinus, gradually widening and deepening, with a rounded-angular profile. The sinus is sharply bounded by rather sharp folds, running...

…also from the beak. The saddle on the dorsal valve also begins at the beak and is likewise sharply delimited from the lateral parts of the valve. Near the anterior margin, on either side of it, lie deep depressions. The saddle is moderately high, flat-topped. Along its middle runs a shallow, distinct depression. The growth lines are very dense, fine, regular.

Dimensions:	length	width	width/length	thickness
	14.5	17	1.17	10.5

The forms closest to this species are Anathyris helmersenii Buch and especially Athyris erbrayi Barrois. The first differs in its straight hinge margin and the development of the shell in width. The second differs only in its somewhat less developed saddle and sinus and in its less inflated valves (comp. 5, pl. VII, fig. 10).

Petz described this species from the Lower Frasnian deposits of the Kuzbass. In our collection A. trapezoidalis belongs to the rare forms. Two specimens of this species come from the northern outcrops of the Lebedyanka Devonian on the Kitat River.

Anathyris resupinata n. sp.

(Table VIII, figs. 21 a–d).

A medium-sized winged shell with a straight hinge margin, only slightly less than the greatest width. The beaks of the valves are close together. Along the hinge margin, on both valves, lie very low areas, bounded by parallel margins; the height of each area is less than 1 mm.

The shell is almost convex-flat. The ventral valve is weakly convex in the umbonal part, elsewhere flat, and in the anterior part broadly and flatly depressed. In this broad, flat depression lies a narrow sinus, bounded by very weakly expressed folds. The sinus does not reach the beak. The dorsal valve is weakly convex. From the very beak there runs a low but quite distinctly delimited, broad saddle. Along the saddle runs a shallow but clear median depression.

The external surface of the valves is covered with dense, fine, concentric growth lines.

Dimensions:	length	width	thickness
	15	34	8

The distinguishing features of this species are the weak convexity of the shell as a whole, and in particular the flatly depressed character of the ventral valve. These features distinguish A. resupinata from the rather closely related species A. phalaena Phill., which is very widely distributed in the Lower Frasnian deposits of Western Siberia. But the form closest to A. resupinata is Anathyris hirundo Phill. This species was established by Phillips (51, 71) on a specimen of unsatisfactory preservation and was later united by Davidson (12, 18) with A. phalaena. Davidson (p. 1, pl. III, fig. 21, 21 a–b), under the name A. phalaena, gives a better illustration of the species A. hirundo than Phillips, but unfortunately does not describe it, considering it a synonym of A. phalaena. Judging from the illustrations, A. hirundo has precisely a very weakly convex shell and, in particular, a flatly depressed ventral valve, by which it comes very close to our species. However, the absence of any satisfactory diagnosis of the species A. hirundo does not permit the Lebedyanka specimens to be identified with it, and I therefore assign them a new specific name.

A. hirundo has been found in the Middle Devonian limestones of Hares-Nose, in South England. A. resupinata was delivered by M. K. Korovin from Mazalovsky Kitat (above the former Shcherbinovskaya mine).

Anathyris simplex n. sp.

(Pl. VIII, fig. 92).

This species is very close to, and undoubtedly related to, the preceding one: the same dimensions and outlines of the shell, the same slight general convexity, and in particular—the plano-concave or flat character of the ventral valve. The principal feature of this species and the character distinguishing it from A. resupinata is the absence of a clearly expressed saddle and sinus, which gives the valves an extremely simple character. The dorsal valve is an evenly and regularly weakly convex surface: the greatest convexity is somewhat above the middle. The ventral valve is slightly convex in the umbonal part, flat on the wings, and plano-concave at the anterior margin.

In typical specimens the saddle and sinus are not expressed at all, but in some specimens they are slightly indicated, although they never attain the fully clear development that occurs in A. resupinata.

Dimensions:

length	width	thickness
15	27	7
14.5	27	8

A. simplex occurs together with A. resupinata.

Anathyris phalaena Phill.

1. Anathyris phalaena: Khalfin. Genus Anathyris Peetz etc., p. 117, pl. IV, figs. 1a—p (synonymy ib.).

In our collection there is only one somewhat damaged ventral valve belonging to this species, the Siberian representatives of which I have characterized more than once.

The normal convexity of the valve and the sharp folds delimiting the strongly developed sinus distinguish this specimen from A. resupinata.

The specimen comes from Mazalovsky Kitat (above the former Shcherbinovskaya mine).

Anathyris athyroides n. sp.

(Pl. VIII, figs. 89a—b, 90a—b).

The shell is inflated, elongated in width. The hinge margin is not quite straight; the angle formed by the hinge margin at the beak of the shell is approximately 140°.

The beak of the ventral valve is high, considerably raised above the hinge margin, curved, and perforated at the end by a round foramen. The sinus begins at the very beak; it is narrow, rather deep, and sharp. It is bounded by sharp folds. The tongue is high.

The dorsal valve is more convex. The saddle begins at the beak, is very strongly developed, and is sharply upturned above the surface of the valve. It is broad, rounded, with steep sides.

The areas are not developed. Along the hinge margin there runs a deep narrow furrow, formed by the steep infolding of the surfaces of the valves near the hinge margin. A similar formation may be seen in the illustration

*9. Izvestiya TPI, vol. 57, issue 1.

A. helmersenii Buch, from the Orel–Voronezh Devonian, cited by Venyukov (74, pl. V, fig. 11).

The outer surface of the valves is covered with growth marks usual for the genus Anathyris Peetz.

Dimensions of the three specimens in my possession:

length	width	thickness
22	14	12
9.2	~12	6
7	11	4.5

Closest to our species is Anathyris peetzi Khalf. (33, 19), occurring in the lower parts of the Upper Devonian of Western Siberia. Anathyris peetzi differs in its perfectly straight hinge margin, larger dimensions, and broader and deeper sinus. From the other species of the genus Anathyris our form differs so substantially that comparisons are unnecessary. The not quite straight hinge margin brings A. athyroides closer to the genus Athyris M’Coy.

Specimens of A. athyroides were found in the northern outcrops along the Kitat River.

Anathyris triloba n. sp.

(Pl. VII, fig. 81).

This is a rather large, peculiarly shaped, inflated shell. In outline the shell is to some degree three-lobed, which is due, on the one hand, to the development of the shell along the straight hinge margin, and, on the other, to the fact that the anterior part of the shell is narrow and fairly long, with depressions lying along its sides. The hinge margin is long (slightly less than the greatest width of the shell). The cardinal angles are rounded.

Both valves are considerably convex, and the character of their convexity is peculiar. The ventral valve resembles a half-cylinder oriented parallel to the hinge margin; along the middle of this half-cylinder, at one edge, there is a small projection that is the beak of the valve, and at the opposite edge—a flat extension of the median lobe. There is no sinus at all. The dorsal valve is for the most part flat, with a median elevation (saddle); near the lateral and anterior margins the surface of the valve bends sharply, almost knee-like, toward the ventral valve. The saddle begins at the beak, is flat, and gradually widens. The anterior part of the valve (“median lobe”) on the side of the dorsal valve is entirely occupied by the saddle.

The beaks of the valves are close together. Along the hinge margin there are very narrow (linear) areas on both valves. The sculpture of the outer surface is very poorly preserved, but insofar as it can be judged, it is usual for representatives of the genus Anathyris.

The shell as a whole is coarse, not quite regular or symmetrical.

Dimensions of the single specimen of this species: width—34, length—22, thickness—16.

The peculiarity of the general form of the shell and the absence of a sinus, in the presence of a well-developed saddle, distinguish this species from all the others. Nearest to it stands A. athyroides mihi, with which, apparently, A. triloba is genetically connected. Both these species, it seems to me, belong to the group of A. peetzi mihi (35, 123).

Anathyris helmersenii Buch.

(Plate VIII, figs. 88a—b).

1. Anathyris Helmersenii: Khalfin. Genus Anathyris Peetz etc., p. 122 (synonymy ib.).

In the cited work the Siberian representatives of the species A. helmersenii are characterized in detail, a species that is known in the upper parts of the Middle Devonian and passes through the entire Frasnian stage. In the Lebedyan Devonian A. helmersenii occurs rarely and is represented by small and very small specimens. In the larger specimens the hinge margin is straight; in the small ones it is not quite straight. The outline of the shell is distinctly pentagonal. The ratio of width to length is about 1.5. The sinus is sharply expressed, begins at the beak, and is bounded by sharp folds. The saddle is also well developed, and the longitudinal depression on it is distinct.

The Ural representatives of this species are the closest (see 68, 56); on the contrary, the Semiluki forms differ considerably. For a comparison with the Siberian Upper Devonian mutations of this species, see the work cited in the synonymy. Athyris trapezoidalis Peetz is also very close; for a comparison of these two species, see Peetz’s description of the species.

Dimensions of some of our specimens:

width	length	thickness
18	12.5	8
11	8	5.5

In a small number of specimens, A. helmersenii was found together with other anathyrids along the Kitat River.

Retzia nana n. sp.

(Plate VIII, figs. 93a—b, 94a—b, 95a—b).

Among Middle and Upper Devonian retziids there is a group of forms very close to one another and possessing such slight differences that the difficulty of separating the species of this group has repeatedly been pointed out in the literature. This group consists of: Retzia prominula Roem., Retzia tulensis Romanowsk., Retzia lopatini Stuck. and Retzia korovini V. Khalf. The differences lie in the outlines of the shell, the degree of development of the sinus, and the number of ribs. Although the existing differences are small, they are constant and have the significance of specific differences—at least until a critical revision of the materials for this group, based on a comparative study of its representatives from various localities. At the present moment I am compelled to add to this group a new member, as close to the others as the latter are to one another, but nevertheless not identical with any of the species of this group.

R. nana is a shell of small size, with equally convex valves and broadly rounded outlines. The width is equal to the length or slightly greater than the latter. The greatest convexity is almost in the middle of the shell, somewhat closer to the hinge margin. The beak of the ventral valve is low and bent. The apical angle is 100°. On the beak there is a small round foramen, beneath which are deltidial plates of the usual type.

In some specimens the sinus is distinctly expressed, forming a shallow depression in which four riblets are placed.

In others, the sinus is scarcely noticeable, but it is usually emphasized by the fact that the furrow between the two middle ribs is developed somewhat more strongly than the others, as is the case in Retzia korovini, var. intermedia V. Khali. (37). The saddle is either barely noticeable or not expressed at all.

The sculpture consists of sharp, regular radial ribs; in small specimens they are rounded, and in larger ones flat-topped. The intervals between the ribs are flatly rounded. The number of ribs, irrespective of the size of the shell, is 18–20 on each valve. The structure of the shell substance is punctate.

Dimensions:	length	width	thickness
	8.5	9.2	5
	5.5	6.2	3
	4.2	4.2	2.5

Of all the closely related species, R. nana differs in its smaller dimensions: adult individuals of our species are almost half the size of adult representatives of the related species. From R. prominula and R. tulensis our form differs in the outlines of the shell: these species have a shell with predominant development in length, which gives it elongate-oval outlines. In the number of ribs and in the development of the sinus, R. nana occupies an intermediate position between these species.

The closest is R. korovini, var. intermedia, entirely analogous in the degree of development of the sinus and in the outlines of the shell, but it also differs by its larger dimensions and smaller number of ribs (12–16 on each valve). Retzia korovini typ., moreover, has no sinus at all. Retzia lopatini Stuck. differs in larger dimensions and a greater number of ribs (24–30 on each valve).

R. nana is represented in our collection by fifteen specimens of excellent preservation. All the specimens come from a single locality—the Kamenushka River (a tributary of the Alchedat).

Retzia lopatini Stuck.

(Pl. VIII, fig. 99).

1. Rhynchonella Lopatini: Stuckenberg. Mém. Acad. Sc. SPB, VII Sér., vol. XXXIV, No. 1, p. 6, Taf. 1, Fig. 5–9.
2. Retzia Lopatini: Petz. Materials for the knowledge of the fauna of the Devonian deposits, etc., p. 125.

This variable form is widely distributed in the Minusinsk Middle Devonian, from where it was described by Stuckenberg. The description and figures given by this author show that R. lopatini varies considerably with respect to the number of ribs and the degree of development of the sinus, and the fluctuations in these respects (as noted in the description of the preceding species) are often the basis for specific divisions within this group of representatives of the genus Rerzia. I believe that within the species R. lopatini there are several varieties not yet distinguished.

The single specimen of this species present in our collection is a shell of rounded outline, measuring: width—10, length—10, thickness—6.2.

The number of ribs is 28 on each valve. The sinus is barely noticeable near the frontal margin; the saddle is not expressed. It differs from the preceding species in the larger size of the shell and in its finer and more numerous ribs.

Petz cites R. lopatini from stringocephalid limestones of the village of Bachaty (southern margin of Kuzbass). Apparently, the distribution of this species is confined to the Middle Devonian. The specimen from the Lower Frasnian deposits of the eastern margin of Kuzbass, described by me (33; 23) under the name R. lopatini, belongs to the species R. korovini V. Khalf.

Retzia cf. prominula Roem.

(Table VIII, figs. 96 a—b, 97 a—b).

Three small specimens in our collection may be provisionally referred to Roemer’s species. The dimensions of these specimens are:

length	width	thickness
7	6.5	4
4.5	4	3
4	4	2.2

The grounds for assigning these specimens to the species Retzia prominula are: the outline of the shell is elongate-oval; the sinus is barely expressed, almost imperceptible; the saddle is not expressed at all; the number of ribs is 20 on each valve. The difference from Roemer’s species is the smaller size, which could be explained by assuming that we have before us juvenile specimens of this species. This explanation, however, is to a great extent artificial, since apparently the Lebedyanskoe representatives of the genus Retzia are generally characterized by small dimensions (only one specimen of R. lopatini is larger than the others), and, of course, it is impossible to admit that in the Lebedyanskoe Devonian only juvenile representatives of this genus occurred. Therefore, a reservation has been made in the identification of these specimens.

The characterized specimens differ from R. nana in the elongate-oval outline of the shell. From R. lopatini they differ also in the smaller number of ribs. Most probably, this is a new species, very close to R. prominula and R. nana. The specimens were found together with R. nana.

Retzia kayseriaeformis n. sp.

(Table VIII, figs. 98 a—c).

A very small, isometric shell of pentagonal outline. The valves are equally convex. The greatest width is in the middle. The apical angle is about 100°. The anterior margin is straight; the outline of the shell forms an almost regular pentagon. The beak of the ventral valve is moderately high, curved; beneath the foramen are deltidial plates of the usual type.

A very characteristic feature is the presence of sinuses on both valves. The sinus of the ventral valve is a broad, distinct, though not deep depression, in which 6 ribs are accommodated. The sinus begins at the beak. The sinus of the dorsal valve likewise begins at the very beak, is also distinctly expressed and as broad as on the ventral valve, but is less distinctly delimited from the lateral parts of the shell.

The sculpture of the external surface consists of thin, regular, rounded radial ribs, 22 in number on each valve. The shell substance is finely punctate.

In our collection there is a single specimen of this species, with the following dimensions:

width	length	thickness
3.5	3.5	2

In external characters our specimen is distinguished from Kayseria lens Phill. by the different character of the sinuses and by the punctate structure of the shell substance. Those representatives of the genus Rhynchospira Hall and Clarke which likewise possess sinuses on both valves (e.g., R. formosa Hall, R. electra Bill., etc.), whose external resemblance to Kayseria lens is mentioned by Hall and Clarke (24, 101), differ from our species too substantially for there to be any need to analyze these differences.

The specimen of R. kayseriaeformis was found together with R. nana.

Atrypa reticularis Linn.

(Plate VIII, Figs. 102, 103, 104.)

Atrypa desquamata Sow.

(Plate VIII, Figs. 100, 101 a—b).

Both these species are widespread in the Lebedyanian Devonian and are represented by typical specimens. The question of their interrelationship has been discussed more than once in the paleontological literature. The differences between them were formulated most fully and definitely by Whidborne (75, 115—116). The vertical and horizontal distribution of these species and their comparison with closely related forms are given by Reed (55, 96—98) and Nalivkin (43, 99).

The dimensions of the Lebedyanian specimens vary within the following limits:

	A. reticularis	A. desquamata
width	50—17	40—20
length	45—17	39—21
thickness	29—7	25—11

In the Devonian of the Kuzbass, A. reticularis is universally distributed.

I have characterized the Lower Frasnian representatives of this species (33, 23—24), which show certain differences from the Lebedyanian ones: the former usually possess a longer, straight hinge margin and always a very weakly developed sinus. A. desquamata is cited by Fletch from the Middle Devonian limestones of the margins of the Kuzbass.

In the Lebedyanian Devonian both these species occur together, but A. reticularis is ubiquitous, whereas A. desquamata has been encountered in quantity at only one locality—on the Alchedat River, near the cemetery.

Atrypa sp. (aff. A. desquamata Sow.)

A small, moderately convex dorsal valve of subquadrate outline.

Dimensions: length—11
width—12

There is no saddle or sinus, but in the center the valve is slightly flattened. The surface of the valve is covered with fine radial ribs, numbering more than 50. The ribs increase in number, chiefly by—

together by intercalation, but some of them also dichotomize. Growth marks are not numerous, weak.

The specimen was found together with A. desquamata, to the finely ribbed representatives of which it is very close; but in A. desquamata the dorsal valve is evenly swollen, with maximum convexity in the center of the valve, whereas the dorsal valve being characterized here is flattened in the center.

A complete identification of our specimen with any species is difficult. For distinguishing a new form, the presence of a single dorsal valve (taking into account the general variability of atrypids) is insufficient.

The specimen comes from the Alchedat River, near the cemetery.

Atrypa sinensis Kayser.

(Table VIII, figs. 105 a—c).

1. Atrypa aspera, var. sinensis: Kayser. Dev. Versteiner. S.-W. China, S. 83, Taf. IX, Fig. 3.
2. Atrypa aspera, var. sinensis: Reed. Dev. Fauna North. Shan States, p. 98, pl. XV, fig. 18.
3. Atrypa aspera: Mc. Magon and Hudleston. Foss. from Hindu-Khoosh, p. 55, pl. III, figs. 4—7.

The shell is isometric, of small size, with a rounded outline. The ventral valve is moderately or considerably convex, with a long, sharp, slightly incurved beak. There is no sinus at all. The dorsal valve is very weakly convex, almost flat. The surface of both valves is covered with coarse, straight radial ribs, dichotomizing and intercalated at varying distances from the beak. The number of ribs along the margin of the shell varies from 20 to 30 on each valve. Sharp, not very numerous growth laminae form spine-like tubercles on the ribs. The number of concentric growth laminae is about 10 on each valve.

Dimensions:

width	length	thickness
15	13.5	6.2

The characteristic features of this species are the flat dorsal valve and the character of the sculpture: sharp, numerous, spinose radial ribs.

Between the specimens of A. sinensis figured by Kayser (l.c.) and the Burmese representatives of this species described by Reed, there are differences, perhaps sufficient for separating the latter as a distinct variety. These differences concern the sculpture: in the Chinese specimens the ribs and growth marks are more numerous and less sharp than in the Burmese ones; in the former the sculpture is, in general, weaker than in the latter. In our collection there are specimens of both types, quite similar to the Chinese and Burmese representatives of the species.

Some specimens from the Upper Devonian of the Hindu Kush, judging from the figures given by Mc. Mahon and Hudleston (see the synonymy), are very close to A. sinensis; unfortunately, the descriptions given by these authors are very brief, and the drawings do not make it possible to judge certain characters.

It is close to Atrypa aspera Schl., which differs in having fewer, coarser ribs and a convex dorsal valve. Still closer is A. spinosa Hall (see, e.g., b, pl. XXIII, figs. 8—9), from which A. sinensis differs only in its flat dorsal valve.

A. sinensis was found at two localities: along the Alchedat River, near the cemetery, and along the Kitat River below the stockyard.

Atrypa tubaecostata Paeck.

1. Atrypa aspera: Venyukov. Fauna of the Dev. Syst. etc., p. 103, Pl. VI, fig. 2.
2. Atrypa reticularis: Walther. N. J. Min., vol. XXIV, p. 287, Pl. XIII, Fig. 18 b, c.
3. Atrypa tubaecostata: Paeckelmann. Oberdev. d. Berg Landes, p. 281, Pl. VI, Fig. 6–7.
4. Atrypa tubaecostata: Paeckelmann. Mitteldev. Massenkalk d. Berg Land. p. 60.
5. Atrypa tubaecostata: Nalivkin. Semiluk. and Voronezh beds, p. 74.

A considerable number of specimens in our collection belong to this species. Its distinctive features are: the equal convexity of the valves; the high, sharp beak of the ventral valve, which makes it possible to see the foramen and the clearly delimited area; the short, straight hinge margin; and the characteristic sculpture. The latter consists of tube-like ribs, separated by broad rounded intervals, and of numerous dense growth marks, which are concentric lamellae overlapping one another like tiles.

Our specimens exhibit all these characters quite distinctly. The hinge margin in our specimens is somewhat longer than in the German ones, though nevertheless considerably shorter than the greatest width of the shell. In this respect our specimens are closer to the Semiluki specimens.

With respect to the degree of development of the sinus and the number of ribs, representatives of A. tubaecostata show strong variability (the number of ribs, according to Paeckelmann, varies from 28 to 56 on each valve). Our specimens have no sinus at all; only one of them shows a weak bend of the frontal margin. The number of ribs in the large specimens is usually from 30 to 40 on each valve (counting along the margin of the valve), rarely more.

Dimensions of our specimens:

width	length	thickness
24	22	13
22	20	11.5
11.5	11	6.5

A comparison of A. tubaecostata with closely related species is given by Paeckelmann (48, 280, 283). It need only be added that finely ribbed specimens of A. tubaecostata show considerable similarity to A. desquamata, and when the outer surface is poorly preserved they are difficult to distinguish from the latter. Atrypa spinosa Hall differs in its smaller number of ribs, different convexity of the valves, and more curved beak.

Atrypa sp. (aff. Atrypa owenensis Webst.)

A small ventral valve of elongate-oval outline, with a sharp beak. Length—10, width—8.5. Along the middle of the valve there runs a low but distinct keel-like elevation, because of which the valve acquires a somewhat roof-like character. The surface of the valve is covered with numerous very fine rounded ribs; their number along the margin of the valve is about 40. A peculiarity of the ribs is their tendency toward intensified dichotomizing: already at a distance of \(1/4\) of the shell length from the beak most of the ribs dichotomize; approximately halfway between the beak and the margin of the valve a secondary dichotomizing takes place. Finally, some riblets dichotomize once more, already close to the margin of the valve. Growth marks are few and rather coarse.

The distinctive features of this specimen are its small size, the fine ribs dichotomizing repeatedly, and the keel-like elevation along the line of symmetry of the valve. Apparently, we are dealing with a new species, standing close to A. aliensis Vern., Atrypa salairica Peetz, Atrypa alticola Frech, and Atrypa owenensis Webster. From A. aliensis our specimen differs

by the presence of a keel, coarser ribs, and sharper growth marks. From A. sulairica—by its greater development in length, considerably coarser ribs, and sharper growth marks. A. alticola has no keel and usually is of larger size. The closest is A. owenensis Webster (16, p. 141, pl. XXVI, figs. 9–11) from the Upper Devonian deposits of the State of Iowa, differing in coarser ribs and growth marks; the ribs in A. owenensis are fewer than in our specimen. From all the species noted above, the described ventral valve differs in the intensified dichotomizing of the ribs.

The specimen was found on the Alchedat River, near the cemetery.

Atrypa spinosa Hall, n. var. nana

(Pl. VIII, figs. 106, 107, 108, 109).

Twelve small specimens present in our collection stand closer to this species than to Atrypa aspera Schloth.

The shell is isometric, with a rounded outline. The apex of the ventral valve is low, slightly bent. There is no sinus at all. In the smallest specimens the valves are equally convex. In the larger ones the ventral valve is slightly convex in the umbonal part and becomes flat near the anterior margin. The dorsal valve is strongly and regularly inflated, without any signs of a fold or sinus.

The sculpture consists of sharp, coarse radial ribs, 12–14 in number on each valve. In most cases the ribs are simple, rarely dichotomizing. The ribs are crossed by dense, numerous lamellar (scaly) growth marks.

Dimensions of the best-preserved specimens:

length	width	thickness
12	13	6
7	7.5	3.2

The closest is A. spinosa, especially the specimens from the Snyder Creek Shale (D₃) of the State of Missouri (6, pl. XX, figs. 8–11; pl. XXIII, figs. 8–9); the only difference is that our specimens are smaller. At the same time, judging from the relative convexity of the valves, it can be said with full confidence that among our specimens there are different age stages, and the specimen with an almost flat ventral valve is apparently a fully adult individual. Nevertheless, it too is of considerably smaller size than ordinary American A. spinosa. A. aspera differs in having a more convex ventral valve and coarser and broader ribs. A. sinensis possesses the reverse relative convexity of the valves, more numerous ribs, and less numerous growth marks.

A. spinosa in North America has a broad distribution, both horizontal and vertical. Schuchert notes (59, 156) that the most typical specimens of this species occur in the upper part of the Middle Devonian (Hamilton group); in lower horizons A. spinosa has more numerous and finer ribs and therefore is difficult to distinguish from A. reticularis, whereas in higher ones (Chemung group), on the contrary, it approaches Atrypa hystrix Hall.

Two small valves have a flat border along the periphery, which is quite usual for representatives of the genus Atrypa. In one of these specimens the ribs continue beyond the shell in the form of short spines with blunt ends.

The Lebedyansk specimens of A. spinosa nana come from the Alchedat River.

List of Brachiopods of the Lebedyan Devonian

Chonetes coronata Contr.
    ” cf. subcancellata Reed.
Productella subaculeata Murch.
    ” spinulicosta Hall.
Stropheodonta asella Vern.
    ” reticularis n. sp.
Douvillina sp.
Leptaena rhomboidalis Wilck.
Schellwienella umbraculum Schl.
Schuchertella chemungensis Conr.
Dalmanella eifeliensis Vern.
    ”     ” var. subtetragona Gür.
    ” sibirica n. sp.
    ” cf. tioga Hall.
Rhipidomella vanuxemi Hall.
Schizophoria striatula Schl.
Kayserella ramosa n. sp.
Uncinulus korovini n. sp.
    ” (?) subsignatus Reed.
    ” (?) concentricus n. sp.
Cryptonella planirostra Hall.
Cryptonella (?) rhomboidea n. sp.
    ” cf. jucunda Hall.
Trigeria (?) lata n. sp.
Spirifer cabedanus Vern. et Arch.
    ” cf. argentarius Meek.
    ” undifer Roem.
    ” martianoffi Stück.
    ” n. sp.
    ” (Hysterolites) cheeheil Kon.
    ”     ”     ” var. alata Stück.
    ”     ” biderexus n. sp.
    ”     ” mesolobus Kor.
    ”     ” semicostalis n. sp.
    ”     ” mirus n. sp.
    ”     ” orthogonalis n. sp.
Spirifer (Delthyris) altschedatiensis Kor.
    ”     ” robustus Barr.
    ” (Delthyris ?) mesocostalis Hall.
    ” (Eoreticularia) aviceps Kays.
    ” (Cyrtospirifer) sp.
Cyrtina heteroclita Defr.
    ”     ” var. multiplicata Dav.
    ”     ” intermedia Oehl.
Merista plebeia Sow.
    ” lacryma Sow.
Meristella nasuta Conr.
    ” yanischewskii n. sp.
Athyris subacuminata n. sp.
    ” concentrica Buch.
    ” fultonensis Swallow.
    ” rugata Dav.
    ” glassi Dav.

Athyris polita Hall.
    ” gracilis Sandb.
    ” circularis n. sp.
    ” cf. triplexioides Oehl.
    ” trapezoidalis Peetz.
Anathyris resupinata n. sp.
    ” simplex n. sp.
    ” phalaena Phill.
    ” athyroids n. sp.
    ” triloba n. sp.
    ” helmersenii Buch.
Retzia nana n. sp.
    ” lopatini Stuck.
    ” cf. prominula Roem.
    ” kayseriaeformis n. sp.
Atrypa reticularis L.
    ” desquamata Sow.
    ” sp. (aff. A. desquamata Sow.)
    ” sinensis Kays.
    ” tubaecostata Paeck.
    ” sp. (aff. A. owenensis Webst).
    ” spinosa Hall, n. var. nana.

Conclusion.

The list of brachiopods of the Lebedyansk Devonian given above contains 75 forms, belonging to fourteen families and twenty-six genera and subgenera. Their distribution by families is extremely uneven. The families Spiriferidae and Athyridae are represented most richly and diversely; together they comprise 44% of all the species present in our collection. Conversely, the families Rhipidomellidae, Schizophoridae, and Mystrophoridae are each represented by only a single species. However, some families, despite an extremely simple species composition, play an outstanding role in the Lebedyansk Devonian in terms of the number of individuals. Thus, for example, Schizophoria striatula, the sole representative of the family Schizophoridae, is one of the most widespread forms of the Lebedyansk fauna. For clarity, the number of species of each family and the degree of its distribution are presented as a diagram in Fig. 5.

Diagram of the distribution of brachiopod families in the Lebedyansk Middle Devonian.

Fig. 5.

The following forms enjoy mass development in the Lebedyansk Devonian: Leptaena rhomboidalis, Schellwienella umbraculum, Dalmanella eifeliensis, Schizophoria striatula, Uncinulus korovini, the group Spirifer cheehiel, Athyris subacuminata, Atrypa reticularis, and Atrypa desquamata. Very numerous are: productellids, Stropheodonta asella, Rhipidomella vanuxemi, Delthyris altschedatiensis, Athyris concentrica, Athyris circularis, the genus Retzia, Atrypa tubaecostata.

Conversely, only single specimens are represented by: Chonetes subcancellata, Kayseria ramosa, Uncinulus (?) subsignatus, Uncinulus (?) concentricus, Trigeria (?) lata, Spirifer undifer, Spirifer martianoffi, Delthyris robusta, Reticularia aviceps, subgen. Cyrtospirifer, Cyrtina heteroclita typ., terebratulids, meristellids, Athyris glassi, Athyris polita, Athyris gracilis, Athyris trapezoidalis, Anathyris phalaena, Anathyris triloba, Retzia kayseriaeformis.

Conclusion.

The list of brachiopods of the Lebedyanskian Devonian given above contains 75 forms, belonging to fourteen families and twenty-six genera and subgenera. Their distribution by families is extremely uneven. The families Spiriferidae and Athyridae are represented most richly and diversely; together they include 44% of all species present in our collection. Conversely, the families Rhipidomellidae, Schizophoriidae, and Mystrophoridae are each represented by only a single species. However, some families, despite an extremely simple species composition, play a prominent role in the Lebedyanskian Devonian in terms of number of individuals. Thus, for example, Schizophoria striatula, the sole representative of the family Schizophoridae, is one of the most widespread forms of the Lebedyanskian fauna. For clarity, the number of species of each family and the degree of its distribution are presented as a diagram in Fig. 5.

Distribution table of brachiopod families
in the Lebedyanskian Middle Devonian.

Fig. 5.

The following forms are massively developed in the Lebedyanskian Devonian: Leptaena rhomboidalis, Schellwienella umbraculum, Dalmanella eifeliensis, Schizophoria striatula, Uncinulus korovini, the group Spirifer cheehiel, Athyris subacuminata, Atrypa reticularis, and Atrypa desquamata. Very numerous are: productellids, Stropheodonta asella, Rhipidomella vanuxemi, Delthyris altschedatiensis, Athyris concentrica, Athyris circularis, the genus Retzia, Atrypa tubaecostata.

Conversely, only single specimens represent: Chonetes subcancellata, Kayseria ramosa, Uncinulus (?) subsignatus, Uncinulus (?) concentricus, Trigeria (?) lata, Spirifer undifer, Spirifer martianoffi, Delthyris robusta, Reticularia aviceps, subgen. Cyrtospirifer, Cyrtina heteroclita typ., terebratulids, meristellids, Athyris glassi, Athyris polita, Athyris gracilis, Athyris trapezoidalis, Anathyris phalaena, Anathyris triloba, Retzia kayseriaeformis.

In the composition of the Lebedyanskaya fauna, new forms predominate, making up 37%. The second most numerous group consists of European forms (30.9%), but the influence of the American fauna is also expressed quite clearly (13.8%). There are few specifically Asiatic forms (not counting the new ones), namely: Chonetes subcancellata, Uncinulus (?) subsignatus, Spirifer martianoffi, Spirifer cheehiel, Spirifer cheehiel alata, Athyris trapezoidalis, Atrypa sinensis. However, among the European and American forms encountered in the Lebedyanskaya Devonian, 24 have previously been indicated or described from various points of the Asiatic continent. On the basis of geography our 65 forms¹ are distributed as follows:

Forms	Number	Percent
European forms	20	30.9%
American forms	9	13.8%
Asiatic forms	7	10.8%
Universally distributed	5	7.5%
New forms	24	37.0%
Total	65	100%

The age of the Lebedyanskaya fauna is determined quite precisely by the presence in it, in large numbers, of representatives of the group Spirifer cheehiel Kon. These spirifers characterize the Zhivetian deposits in China. In Siberia they occupy the same stratigraphic position. The author of this article had occasion to observe, in Northwestern Altai, a section of a single conformable Devonian sequence in which a bed with Sp. cheehiel lies beneath the Lower Frasnian deposits.

However, if, in order to confirm the Stringocephalus age of the Lebedyanskaya fauna, we turn to the remaining brachiopods of our list, then at first glance we shall not obtain convincing evidence. First of all, we must state the absence from our list of such popular Stringocephalus forms as Stringocephalus burtini and Uncites gryphus, which are already widely distributed in Turkestan and Kashgaria. The absence of these forms is especially noteworthy because, in the Lebedyanskaya fauna, a significant percentage is made up of European forms, which give the entire fauna a certain European aspect. Moreover, if we exclude from consideration the native (Siberian—Spirifer martianoffi, Retzia lopatini) and new forms, then among the remainder we shall find almost exclusively such forms as are distributed both in the Zhivetian stage and in lower Devonian horizons; that is, typical Zhivetian forms (with the exception of the group Sp. cheehiel) are generally absent from the Lebedyanskaya fauna. The few species, such as Athyris rugata, Athyris gracilis, which constitute an exception, occur in the Lebedyanskaya fauna as single specimens and can hardly be regarded as sufficiently reliable guide forms.

Thus, in determining the age of the Lebedyanskaya fauna, the following characteristics must be taken into account:

1. An abundance of native and new forms.
2. An abundance of representatives of the group Spirifer cheehiel.
3. An abundance of European forms.
4. The absence of reliable Stringocephalus species, in particular Stringocephalus burtini and Uncites gryphus.
5. Among the European forms, a decisive predominance of those which are distributed both in the Stringocephalus horizon and in lower Devonian horizons.

These characteristics, however, are not exclusively peculiar to the Lebedyanskaya fauna: such, in general, is the fauna of the Stringocephalus deposits

Western Siberia (the Minusinsk Basin, Altai). For the correct interpretation of these circumstances and the correct determination of the age of the fauna, it is necessary to analyze extensive material on the paleontology and geology not only of Kuzbass, or even of Western Siberia, but also of adjacent regions and countries. This work has been carried out by me in a special article¹, and therefore here I can confine myself only to the conclusions that I obtained; these conclusions are as follows.

1) In the West Siberian Devonian, deposits characterized by a fauna with Spirifer cheehiel or, in abbreviated form, the cheehiel fauna, are widely distributed.

2) The Cheehiel fauna of Siberia is of Stringocephalus age.

3) The absence in the Siberian cheehiel fauna of Givetian cosmopolitans (in particular—Stringocephalus burtini) is explained by the isolation of the West Siberian Givetian basin from the seas of Europe and Central Asia.

4) The abundance of endemic forms (in particular—representatives of the group Spirifer cheehiel) is explained by this same isolation; there was direct communication between the West Siberian and South Chinese basins.

5) The similarity of the Givetian fauna of Siberia to the European fauna is inherited from the Eifelian epoch, when the Siberian basin had broad communication with the western seas and was populated by fauna migrating eastward.

Comparing the Lebedyanskoye deposits with deposits of the same age in the nearest regions, one must first of all consider the Stringocephalus stage on the southwestern margin of Kuzbass (the area of Bachaty Station). From these deposits, represented by thick bluish-gray limestones, Petz cites (51, 297) 28 species of brachiopods, of which 12 are common to the brachiopods of the Lebedyanskoye Devonian. Nevertheless, our fauna differs sharply from that of Bachaty by the presence in the former of a diverse and richly represented group of Spirifer cheehiel, completely absent from the Bachaty fauna. Another sharp difference of our fauna is the abundance in it of diverse representatives of the genera Athyris and Anathyris, entirely absent from the fauna of the village of Bachaty; the same must also be said with respect to the dalmanellids. On the other hand, in our fauna the pentamerids (which occur in the Bachaty fauna) are completely absent.

These differences in the fauna of the localities being compared may be due either to differences in stratigraphic position or to facies differences. The possibility is not excluded that the faunas being compared belong to different horizons of the Givetian stage, which seems to me most probable.

Along the northeastern margin of Kuzbass, deposits of the productive suite of the Barzas district are coeval with the Lebedyanskoye deposits. As is known, these deposits are overlain by lower Frasnian limestones with a fauna of Spirifer disjunctus Sow. s. str., Spirifer tenticulum Vern., Anathyris phalaena Phill., Douvillina dutertrii Murch. and some others. This association of forms characterizes the lowest beds of the Frasnian stage; i.e., the productive sapropelite sequence of the Barzas district belongs in part to the uppermost Givetian stage. As established above, the Lebedyanskoye Devonian is of the same age. Hence follows the conclusion: the Lebedyanskoye Devonian is stratigraphically equivalent to part of the Barzas productive sequence.

The differences between the synchronous deposits of the Barzas and Lebedyanskoye districts are facies differences: the productive Barzas sequence consists of entirely nearshore deposits, which, as one moves—

deposits from the shoreline of the Givetian basin westward are replaced by sediments of a shallow, but open, marine basin—the deposits composing the Lebedyan Devonian.

Along the northwestern margin of Kuzbass, in the Zarubino district, according to Tyzhnov (65¹, 25), beneath the Lower Frasnian deposits lies the Zarubino formation, composed in its lower part of limestones, and in its upper part of shales and sandstones; from the latter Tyzhnov records Spirifer cf. cheehiel, Atrypa sp., Stropheodonta interstrialis, mollusks, trilobites, and corals.

In the neighboring Minusinsk Basin, the Givetian deposits contain a poorer fauna than the Lebedyan, but, like the latter, one characterized by an abundance of spirifers of the Spirifer cheehiel group. A short list of brachiopods determined from these deposits (15¹, 26) contains almost 50% of forms common to the Lebedyan fauna.

Very close to the Lebedyan deposits in the fauna contained in them are the Givetian deposits of the Altai. Being very widely developed, these deposits at various localities in the Altai present a number of facies features (36), but everywhere they contain, in large numbers, spirifers of the Spirifer cheehiel group and a number of other forms common to the Lebedyan fauna. Especially close in brachiopod fauna to the Lebedyan Devonian are the Givetian deposits of the Korgon Range: the 13 species of brachiopods known to me from this locality are all, without exception, common with the Lebedyan brachiopods.

In Kazakhstan, according to Kassin (26¹, 89), the Givetian deposits constitute a suite composed of dark-gray and yellowish-gray shaly sandstones with frequent interbeds of marls and limestones, i.e., in lithological composition very close to the Lebedyan Devonian. However, the fauna of Kazakhstanian D²₂, judging from the short list of brachiopods given by Kassin, differs substantially from the Lebedyan, and first of all by the absence of Spirifer cheehiel. Common with the Lebedyan fauna are: Atrypa reticularis, Productella spinulicosta, Productella ex gr. subaculeata, Spirifer undifer, Athyris ex gr. concentrica, Dalmanella aff. tioga, Schuchertella ex gr. umbraculum.

The Givetian deposits of Turkestan, with the exception of Atrypa reticularis, contain no forms in common with the Lebedyan brachiopod fauna.

With these brief comparisons of the Lebedyan fauna with faunas close to it stratigraphically and geographically I shall conclude; these questions have been analyzed by me in detail in a special article on the Spirifer cheehiel group.

References Cited

1. Asselberghs, E. Descr. d’une faune frasn. infér. de Namure. Bull. Soc. Belge G. P. et H., vol. XXVI. 1912–13.

2. Assmann, P. Fauna d. Erbslochgraun bei Densberg im Kellerwald, T. I. Brachiopoden. Jahrb. k. preuss. geol. L.—A., Bd. XXXI. 1910.

3. Barrande, J. Syst. silur. de la Bohême, vol. V. 1879.

4. Barrois, Ch. Recherches sur les terr. anciens d. Asturie et de la Galice. Mém. Soc. géol. du Nord, t. II. 1882.

5. Barrois, Ch. Faune du calcaire d’Erbray. Mém. Soc. géol. du Nord, t. III. 1889.

6. Branson, E. B. The Devonian of Missouri. Miss. Bureau of Geol. and Mines, vol. XVII, ser. II. 1922.

7. Branson, E. B. and J. S. Williams. Fauna of the Middle Devon of Southeastern Missouri. In Branson’s “Dev. of Missouri.” 1922.

8. Bublichenko, N. L. On certain Middle Devonian brachiopods of the Altai. Izv. Geol. Kom., vol. 46. 1928.

9. Clarke, J. M. Fosseis Devonianos do Paraná. Serv. Geologico e Mineralog. do Brasil. 1913.

10. Clarke, J. and Ch. Swartz. Brachiopoda from Upp. Devon. of Maryland. Maryl. Geol. Surv. (Middle and Upp. Dev.). 1913.

11. Dahmer, G. Fauna d. obersten Koblenzschichten v. Mandeln bei Dillenburg. Jahrb. kön. preuss. geol. L.—A., Bd. XXXVI. 1915.

12. Davidson, Th. Monograph of the Brit. foss. Brachiopoda, vol. III. Devonian and Silurian. Palaeontogr. Society. 1864–1871.

13. Davidson, Th. Monogr. of the Brit. fossil Brachiopoda, vol. V. Supplements. Palaeontogr. Society. 1882–1884.

14. Drevermann, F. Fauna d. Unterkoblenzschichten v. Oberstadtfeld bei Daun in d. Eifel. Palaeont., Bd. XLIX, Lief. II. 1902.

15. Drevermann, F. Fauna d. oberdevon. Tuffbreccie von Langenbaush bei Heiger. Jahrb. k. pr. geol. L.—A., Bd. XXI. 1900–1901.

15’. Edelstein, Ya. Geological sketch of the Minusinsk Basin and adjoining parts of the Kuznetsk Alatau and the Eastern Sayan. 1932. Essays on the Geology of Siberia.

1. Fenton, C. L. and M. A. Fenton. Stratigr. and Fauna of Hackberry Stage of the Upp. Dev. Contrib. from Mus. of Geol. Univ. Mich., v. I. 1924.

2. Frech, F. Geologie der Umgegend von Haiger bei Dillenburg (Nassau). Abh. kön. pr. geol. L.—A., Bd. VIII, Ht. 3. 1888.

3. Girty, G. H. The Guadalupian Fauna. Un. St. Geol. Surv., Prof. Papers. 58. 1908.

4. Grabau, A. W. Stratigraphy of China. Geol. Surv. China. 1922–24.

5. Grabau, A. W. Devonian Brachiopoda of China. Palaeont. Sinica, ser. B, vol. I, f. 2. 1924.

6. Gürich, G. Palaeozoicum des Polnischen Mittelgebirges. Zap. SPb. Mineral. Soc., ser. II, pt. 32. 1896.

7. Hall, J. Palaeont. New York, vol. III. 1861.

8. Hall, J. Palaeont. New York, vol. IV, pt. I. 1867.

9. Hall, J. and J. Clarke. Palaeont. N. Y., v. VIII, Pts. I–II. 1892–1894.

10. Hermann, F. Das hercynische Unterdevon bei Marburg a. L. Jahrb. d. kön. preuss. geol. L.—A., Bd. XXXIII. 1912.

11. Holzapfel, E. Das obere Mitteldevon. Abhandl. kön. preuss. geol. L.—A., N. F., Ht. 16. 1895.

12. Kassin, N. General geological map of Kazakhstan. Proceedings of the Main Geological-Prospecting Administration, issue 110. 1931.

13. Kayser, E. Devonische Versteinerungen aus dem südwestlichen Chine. 1883.

14. Kayser, E. Fauna d. ältesten Devon-Ablagerungen des Harzes. Abhandl. d. geologisch. Specialkarte usw., Bd. II, H. 4. 1878.

15. Kayser, E. Beitr. z. Kenntniss v. Oberdevon und Kulm am Nordrande d. rhein. Schiefergeb. Jahrb. k. pr. geol. L.—A. 1881.

16. Kayser, E. Die Brachiop. des Mittel-und Ober-Devon der Eifel. Zeitschr. d. deutsch. geol. Ges., Bd. XXIII. 1871.

17. Kindle, E. M. The Onondaga Fauna of the Alleghany Region. Bull. U. S. Geol. Surv., 508. 1912.

18. Khalfin, L. Upper Devonian brachiopods of the Cherep locality. Tr. N.-I. Ug. In-ta Vostuglya, ser. G, No. 2. 1932.

19. Khalfin, L. Lower Frasnian brachiopods of the margins of Kuzbass. Izv. Zap.-Sib. Geol.-Razv. Tresta, vol. XII, No. 2. 1932.

20. Khalfin, L. Upper Devonian of the village of Zharkovsky on the Ye River. Proceedings of the Scientific-Research Coal Institute of Kuzbassugol. 1933.

21. Khalfin, L. The genus Anathyris Peetz in the Siberian Devonian. Collection on the Geology of Siberia. 1933. Tomsk.

1. Khalfin, L. Materials on the stratigraphy of the Devonian deposits of Altai. Mat. po geol. Zap. Sib. Kraya, No. 20. 1935.

2. Khalfina, V. Upper Devonian brachiopods and pelecypods of the village of Yaya—Petropavlovskoye (Manuscript). 1933.

3. Koninck, L. Notice sur deux espèces de Brachiopodes du Terr. Paléoz. de la Chine. Bull. Acad. de Belgique, t. XIII. 1846.

4. Korovin, M. K. Essay on the geological structure and mineral resources of the Tomsk district. 1927. Tomsk.

5. McMahon and Hudleston. Fossils from the Hindu Khoosh. Geol. Magazine. New ser., vol. IX, 1902.

6. Mansuy, H. Contribution à la carte géologique de l’Indo-Chine. Paléontologie. 1908.

7. Nalivkin, D. The Semiluki and Voronezh beds. Izv. Glavn. Geol.-Razv. Upr., t. XLIX, No. 1. 1930.

8. Nalivkin, D. Brachiopods of the Middle and Upper Devonian of Turkestan. Tr. Geol. Kom., new ser., issue 180. 1930.

9. Oehlert, D. Étude sur quelques fossiles dévon. de l’Ouest de la France. Ann. de Sci. géol., t. XIX. 1886.

10. Oehlert, D. Fossiles dévoniens de Santa Lucia. Bull. Soc. géol. France, 3, sér., t. XXIV. 1896.

11. Oehlert, D. Sur le Dévonien des environ d’Angers. Bull. Soc. géol. France, 3 sér., t. XVII. 1988—1889.

12. Öpik, A. Brachiopoda Protramata der Estländischen Ordovizischen Kukruse-Stufe. Public. of geol. Instit of Univers. of Tartu, No. 20. 1930.

13. Paeckelmann, W. Das Oberdevon des Bergischen Landes. Abhandl. d. kön. preuss. Geol. L.—A., N. F., Ht. 70. 1913.

14. Paeckelmann, W. Der mitteldevon. Massenkalk des Bergischen Landes. Abhandl. d. preuss. geol. L.—A., N. F., Ht. 91. 1922.

15. Péneaux, J. Études sur le Dév. de la basse-Loire. I. Faciès schisteux du Dév. moyen de Chalonnes. Bull. Soc. d. Sci. Natur. l’Ouest Fr., sér. IV, t. VII. 1927.

16. Petz, G. Materials toward knowledge of the fauna of the Devonian deposits on the margin of the Kuznetsk coal basin. Trudy geol. chasti kab., t. VI. 1901.

51₁. Phillips, J. Figures and Descriptions of the Palaeszoic Fossils of Cornwall, Devon, and West Sommerset. 1841.

1. Prosser, C. S. and Kindle, E. M. Brachiopoda from Upp. Dev. of Maryland. Mar. Geol. Surv. (Middle a. Upp. Dev.). 1913.

2. Quiring, H. Zusammenst. d. Strophomeniden d. Mitteldevon d. Eifel nebst Beiträg. z. Kenntn. d. Wanderbeweg. d. Brach. Eifeldevo. Neues Jahrb. M. G. P., Bd. I. 1914.

3. Radugin, K. Materials on the stratigraphy of the northern margin of Kuzbass. Coelenterata of the Middle Devonian from the vicinity of the village of Lebedyanskoye. (In press).

4. Reed, C. Devon. Faunas of the North. Shan States. Palaeont. Ind., n. s., v. II, m. 5. 1908.

5. Roemer, F. A. Beiträge zur geologischen Kenntnis des nord-westlichen Harzgebirges. Palaeontographica, Bd. III. 1854.

6. Sandberger G. und F. Sandberger. Die Versteinerungen des rheinischen Schichtensystems in Nassau. 1856.

7. Schnur, J. Zusammenstell. und Beschreibung sämmtlicher im Uebergangsgebirge d. Eifel vorkommenden Brachiopoden. Palaeont., t. III. 1854.

8. Schuchert, Ch. Synopsis of American foss. Brachiopoda. Bull. U. S. Geol. Surv., No. 87. 1897.

9. Scupin H. Die Spiriferen Deutschlands. Paleont. Abhandl. v. Dames u. Koken, Bd. VIII, Ht. 3. 1901.

10. Sobolev, D. Devonian deposits of the Grzegorzewice—Skały—Włochy section. Izv. Varshavsk. Politekhn. In-ta, issue II. 1903—1904.

11. Sobolev, D. The Middle Devonian of the Kielce-Sandomierz Range. Mater. dlya geol. Rossii, t. XXIV, 1909.

12. Stuckenberg, A. Mater. z. Kenntn. d. Fauna d. devonisch. Ablager. Sibiriens. Trudy SPb. Ak. Nauk, VII ser., t. XXXIV, No. 1. 1886.

13. Thomas, J. Neue Beiträge z. Kenntnis d. devonisch. Fauna Argentiniens. Zeitsch. deutsch. geol. Ges., t. 57. 1905.

14. Thomas, J. The British Carboniferous Orthotetinae. Mem. Geol. Surv. Gr. Br., v. 1, pt. 2. 1910.

15. Tyazhnov, A. Materials on the stratigraphy and tectonics of the Devonian deposits of the northwestern margin of Kuzbass. Izvestiya Zap.-Sib. Geol.-Razv. Upr., t. XI, issue 1. 1931.

16. Tolmachev, I. P. The genera Orthotetas Fisch., Streptorhynchus King and related forms of the subfamily Orthotetinae Waag.

17. Chernyshev, F. Materials for the study of the Devonian deposits of Russia. Trudy Geol. Kom., t. I, No. 3. 1884.

18. Chernyshev, F. Fauna of the Lower Devonian of the western slope of the Urals. Trudy Geol. Kom., t. III, No. 1. 1885.

Izv. TIII, t. 57, issue 1. 10.*

1. Chernyshev, F. Fauna of the Middle and Upper Devonian of the western slope of the Urals. Transactions of the Geological Committee, vol. III, no. 3. 1893.
2. Verneuil, E. Paléontologie de la Russie. 1845.
3. Verneuil, E. et d’Archiac. Notes sur les fossiles du terrain paléozoïque des Asturie. Bull. Soc. géol. Fr., sér. II, v. II. 1844—1845.
4. Walcott, Ch. Palaeont. of the Eureka District. Monogr. U. S. Geol. Surv., v. XIII. 1884.
5. Walther, K. Beitr. zur Geologie und Paläontologie des älteren Paläozoicum in Ostthüringen. N. Jahrb. M. G. P. 1907.
6. Venyukov, P. Sediments of the Devonian system in the Mugodzhar Mountains. Transactions of the St. Petersburg Society of Naturalists, vol. XXIII. 1895.
7. Venyukov, P. Fauna of the Devonian system of northwestern and central Russia. 1886.
8. Whidborne, G. Monogr. of the Devon. Fauna of the South of England, vol. II. 1892.

EXPLANATIONS OF THE PLATES

Plate I

Fig. 1. Stropheodonta asella Vern. Ventral valve; outline of the shell.
Fig. 2. Idem. Ventral valve; internal structure.
Fig. 3. Idem. Ventral valve.
Fig. 4. Idem. View of the shell from the side of the dorsal valve; character of the interarea; sculpture. Enlarged.
Fig. 5. Idem. Dorsal valve; internal structure; sculpture. Enlarged.
Fig. 6. Stropheodonta reticularis n. sp. Ventral valve.
Fig. 7. Leptaena rhomboidalis Wilk. View of the shell from the side of the dorsal valve; numerous concentric wrinkles.
Fig. 8. Idem. Specimen with few concentric wrinkles; view from the side of the ventral valve.
Fig. 9. Idem. Internal mold of the ventral valve.
Fig. 10. Douvillina sp. Internal surface of the ventral valve.

Plate II

Fig. 11 a—b. Schellwienella umbraculum Schl. a—view from the side of the dorsal valve; b—profile.
Fig. 12. Idem. Internal mold; a—from the side of the ventral valve, b—from the side of the dorsal valve.
Fig. 13. Idem. Internal surface of the ventral valve.
Fig. 14. Idem. Dorsal valve; sculpture.
Fig. 15. Schuchertella chemungensis Conr. Ventral valve.
Fig. 16. Dalmanella eifeliensis Vern. a—view from the side of the dorsal valve, b—from the side of the ventral, c—from the side of the hinge margin.
Fig. 17. Idem. Internal surface of the dorsal valve.
Fig. 18. Idem. Internal surface of the ventral valve.
Fig. 19. Dalmanella sibirica n. sp. a—view from the side of the dorsal valve, b—from the side of the hinge margin.
Fig. 20. Dalmanella eifeliensis Vern. var. subtetragona Gür. a—view from the side of the ventral valve, b—from the side of the dorsal, c—from the side of the interarea.
Fig. 21. Rhipidomella vanuxemi Hall. a—view from the side of the ventral valve, b—from the side of the dorsal.

Plate III

Fig. 22. Schellwienella umbraculum Schl. Internal surface of the ventral valve.
Fig. 23. Idem.
Fig. 24. Dalmanella sibirica n. sp. a—view from the side of the ventral valve, b—in profile, c—from the side of the dorsal, d—from the side of the interarea.
Fig. 25. Idem. Internal surface of the ventral valve.
Fig. 26. Idem. Internal surface of the dorsal valve.
Fig. 27. Schizophoria striatula Schl.
Fig. 28. Idem. Young specimen.
Fig. 29. Idem. Internal mold of the ventral valve.
Fig. 30. Kayserella ramosa n. sp. a—view from the side of the dorsal valve, b—from the side of the ventral, c—from the side of the hinge margin.
Fig. 31 a—b. Uncinulus korovini n. sp.
Fig. 32 a—d. Idem. Another specimen.
Fig. 33. Idem. Specimen with three ribs in the sinus.
Fig. 34 a—b. Idem. Specimen with five ribs in the sinus.

Fig. 91 a–d. Anathyris [[unclear: species epithet]], n. sp.
Fig. 92. Anathyris simplex, n. sp.
Figs. 93–95. Retzia nana, n. sp.
Figs. 96–97. Retzia cf. prominula Roem.
Fig. 98 a–c. Retzia kayseriaeformis, n. sp.; c—enlarged 4 times.
Fig. 99. Retzia lopatini Stuck.
Figs. 100–101. Atrypa desquamata Sow.
Figs. 102–104. Atrypa reticularis L.
Fig. 105 a–c. Atrypa sinensis Kays.
Figs. 106–109. Atrypa spinosa Hall, n. var. nana.
Fig. 110 a–b. Atrypa tubaecostata Paeck.

Responsible editor: Prof. M. A. Usov.
Technical editor: A. F. Laletin.

Tomsk, Regional Territorial Publishing House No. 1227, 1938.
Sent to production 26/VIII-1937.
Signed for printing 9/IX-1938.
Format: 176 × 250/16.

Volume: 9¼ printed sheets; author’s sheets 12.8.
Printing order No. 1, printed sheet [[unclear: 02176]].
Print run 500 copies.
Order No. 3761-37.

Tomsk, printing house of the publishing house “Krasnoe Znamya,” Sovetskaya St. [[unclear: number]].

Table 1

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10.

Plate II

Fig. 11 — a, b

Fig. 12 — a, b

Fig. 13

Fig. 14

Fig. 15

Fig. 16 — a, b, c

Fig. 17

Fig. 18

Fig. 19 — a, b

Fig. 20 — a, b, c

Fig. 21 — a, b

Plate III

Fig. 22

Fig. 23

Fig. 24

Fig. 25

Fig. 26

Fig. 27

Fig. 29

Fig. 30

Fig. 31

Fig. 32

Fig. 33

Fig. 34

Fig. 35

Fig. 36

Fig. 37

Fig. 38

Plate IV

a b c

Fig. 39

Fig. 40

Fig. 42

b d

Fig. 43

c

a b

Fig. 41

a

a

b

c

Fig. 45

d

Fig. 44

Fig. 46

Fig. 47

Plate V

Fig. 48.

Fig. 49.

a

b

Fig. 50

c

Fig. 51

a

b

a

b

Fig. 52.

Fig. 53.

Fig. 54

Fig. 55.

Fig. 56

Plate VI

Fig. 57

Fig. 58

Fig. 59

Fig. 60

Fig. 61

Fig. 62

Fig. 63

Fig. 64

Plate VII

Fig. 65

Fig. 66

Fig. 67

Fig. 68

Fig. 69

Fig. 70

Fig. 71

Fig. 72

Fig. 73

Fig. 74

Fig. 75

Fig. 76

Fig. 77

Fig. 78

Fig. 79

Fig. 80

Fig. 81

Plate VIII

Fig. 82
Fig. 83
Fig. 84
Fig. 85
Fig. 86
Fig. 87
Fig. 88
Fig. 89
Fig. 90
Fig. 91
Fig. 92
Fig. 93
Fig. 94
Fig. 95
Fig. 96
Fig. 97
Fig. 98
Fig. 99
Fig. 100
Fig. 101
Fig. 102
Fig. 103
Fig. 104
Fig. 105
Fig. 106
Fig. 107
Fig. 108
Fig. 109
Fig. 110

1. “The Siberian Devonian and the group Spirifer cheehiel Kon.” Proceedings of the Tomsk Industrial Institute named after S. M. Kirov, vol. 55, issue III. ↩↩↩↩↩↩

2. See: L. L. Khalfin. The Siberian Devonian and the group Spirifer cheehiel Kon. Izvestiya of the Tomsk Industrial Institute named after S. M. Kirov, vol. 57, 1937. ↩