gJLfi A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA BY E. C. CASE Junior Professor of Historical Geology and Paleontology, University of Michigan WASHINGTON, D. C. Published bv the Carnegie Institution or Washington 1911 CjCs CARNEGIE INSTITUTION OF WASHINGTON Publication No. 145 Copies of this Book «r«re first issue tpedrt appean in Cope't litti of iflti and 18SS, but after that it not litted by him, ai it became apparent that it waa indeterminate . SYSTEMATIC REVISION 19 MeaiuTemtnts — Continued. "No. I, dorsal vertebra of the smaller individual — Continued. „ M Vertical extent of extremity of diapophysis 0.036 Diameter of centrum: Anteroposterior 026 Transverse 027 Width between inferior extremities of tubercular facets of diapophyses . . .066 Width between extremities of zygapophyses 082 Length between extremities of zygapophyses 042 " No. 2, a larger individual. "Total elevation 130 Diameter of centrum: Anteroposterior 029 Transverse .043 Vertical 039 Extent of ^gapophyses 102 Elevation of neural spine 026" Diadectes latibuccatus Cope. Diadectes Cope, Proc. Am. Phil. Soc., vol. xvii, 1878, p. 505. Empedocles Cope, Am. Nat., vol. XIV, 1880, p. 304. Empedias Cope, Proc. Am. Phil. Soc., vol. xx, 1883, p. 634. Empedias Cope, Proc. Am. Phil. Soc., vol. xxxiv, 1896, p. 442. Diadectes Cope, Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 131. Type: A fragmentary maxillary bone. No. 4377 Am. Mus, Nat. Hi.st. Cope Coll. From Texas. Original description: "On comparison with the corresponding portion of the jaw of D. sideropelicus, the following characteristic marks appear: The tooth line diverges much more strongly inwards from the maxillary border in theZ). latibuccatus, leaving a wide groove between the two. This groove is separated by a narrow horizontal partition from a corresponding one on the superior face of the same element, and its surface is ^^[ longitudinally roughened. The teeth are closely placed, and the series turns with the anterior extremity of the C.*^^.?***^^^^^^^) jaw, abruptly inwards. The transverse diameter of the /VmV K^ — teeth lessens to just posterior to the point of curvature, so that their section is nearly round; at and anterior to the curve, the wide transverse diameter is resumed, the Fig. 2.— Anterior half of right maxillary last alveolus preserved making an angle of 45° with oiD.iatibucca,u,. x |. , ■ , ^ ■ /- I • T-i 1 Type No. 4-177 Am. Mus. those m the posterior part of the jaw. 1 he external surface of the maxillary bone is roughened, as is also the case in the D. sidero- pelicus with coarser and finer irregular impressions, fossae, and grooves. " Measurements. "Width of jaw at ninth tooth from curve O.036 Width of ninth tooth from curve on Width of fourth tooth from curve 006 Width of tooth at curve 008 Width of third tooth anterior to curve oio Width of jaw at curve 019 Elevation of alveolar part of jaw 018 Three teeth in 015" In the "American Naturalist" for 1880 Cope referred this species to the genus Empedocles, apparently having decided that the anterior teeth were incisors and not canines. 20 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA In the "Proceedings of the American Philosophical Society" for 1883 the name Empedias is used, as Empedocles was found to be preoccupied. In this paper Cope gives additional characters of the species: "The species of Empedias forms a series which differs from Diadectes in a successive widening of the crowns of the teeth and diminution in number. Thus the E. (written Z).) phaseoltnus is nearest to the Diadectes; E. (written D.) molaris succeeds it, and in E. fissus we have the molariform character most strongly de- veloped. In the E. lattbuccatus, on the other hand, the diminution of the transverse extent of many of the teeth and the areolar sculpture of the superior surface of the cranium points in the direction of the genus Chilonyx. The species of Empedias may easily be distinguished as follows: "1. Surface of the skull divided by grooves into areae. Superior teeth, 16 on each side, a number on each end of the maxillary bone of little trans- verse extent E. lattbuccatus II. Surface of the skull uniformly rugose. Superior teeth narrower, 16 on each side, the last one small, sphenoid flat, pterygoids narrow E. phaseoltnus Superior teeth wider, 14 on each side, the last one smaller, the sphenoid keeled medially, pterygoids wide E. molaris Superior teeth wider, 14 on each side, the last the largest, sphenoid not keeled . . .£. fissus." In 1896 the genera of the Diadectidce were redefined and the E. latibuccatus with the species phaseolinus was restored to the genus Diadectes. Revised description: It is admittedly dangerous to form species in vertebrate paleontology, and especially is this true when dealing with such distorted material as occurs in the beds of Texas, where almost every specimen could be described as a new species — or with a little more latitude almost every specimen of a genus could be retained in a single species. The teeth are more apt to present determinable charac- ters and the foregoing discriminations have been based entirely upon them. In the type specimen oi D. latibuccatus only the bases of the teeth are preserved and in the second specimen used by Cope in his descriptions, No. 4353 Am. Mus. Nat. Hist. Cope Coll., but a single one near the posterior end of the series has any portion of the crown preserved. This tooth looks something like those oi D. biculminatus, but it is very uncertain. The larger number of teeth, seventeen, in the maxillary, and the more numerous smaller teeth with nearly round section at the base, in the region of the maxillary-premaxillaiy suture, are the only distinguishing characters. Diadectes maximus Case. Bull. Am. Mus. Nat. Hist., vol. xxviii, art. xvii, 1910, p. 174. Type: Three large vertebrae. No. 4392 Am. Mus. Nat. Hist. Cope Coll. From Texas. A large number of isolated bones in different collections indicate the presence of a very large member of the genus Diadectes. Size alone, however, is not sufficient to indicate specific difference in the reptilia where growth is practically continuous through life. These vertebrae, from the posterior portion of the column, show a distinct difference from the other members of the genus in the position of the hyposphene and hypantrum. The faces are nearly horizontal instead of being sharply oblique. Measurements. mm Distance from bottom of posterior face of centrum to base of spine . 146.5 Height of the posterior face of the centrum 58.5 Length of bottom of centrum 48 Width acroM pocterior zygapophyses 140 SYSTEMATIC REVISION 21 An anterior caudal vertebra, field No. 252 Am. Mus. Nat. Hist, collection of 1908, of appropriate size to go with the type specimens, measures 182 mm. from the base of the centrum to the top of the spine. The width across the transverse processes to the point of origin of the ribs is 83 mm. Fig. 3. — Doisai mxchn of D. maximus. x f • Type No. 4392 Am. Mus. a, anterior view; b, posterior view. Genus DIASPARACTUS Case. Diasparactus zenos Case. Bull. Am. Mus. Nat. Hist., vol. xxvni, att. xvii, 1910, p. 174. Type: A few connected vertebrae from the posterior portion of the precaudal series. No. 4797 Am. Mus. Nat. Hist. Cope Coll. From New Mexico. The vertebrae are the last presacrals and two sacrals. They are characterized by the small size of the centra compared with the height and width of the neural arch and zygapophyses. The transverse processes are so short that they do not extend out from the centrum as far as the zygapophyses. The last perfect vertebrae of the series, reckoned as the first sacral, shows a peculiar abnormal condition; the transverse process of the right side is very small and there is no face for the attach- ment of a rib, on the left side the transverse process is large but very short and there is a large face for a sacral rib. An imperfect vertebra behind this one shows a reverse of this condition; this is evidently a case of abnormal attachment of the pelvis. Fio. 4. — Vertebra of DifljparurtBj Knoj. X J. Type No. 4797 Am. Mui. a, lateral view of three posterior dorsals; 6, posterior view of a vertebra. The first presacral has only a very short transverse process without any face for the attachment of a rib. The second has a very short face on the transverse process; this face is inclined forward as in Diadectes, but only very slightly so, and the upper 22 A REVISION OK THE C0TYL08AURIA OF NORTH AMERICA end only very slightly overhangs the lower. In Diadectes the face is inclined sharply downward and forward. In the more anterior vertebrae the face on the transverse process grows in length, but the process itself remains so short that it may almost be considered as absent and the articular face attached to the posterior surface of the anterior zygapophysis. Measurements. „„ nun Transverse diameter of a centrum at the middle . 23 Transverse diameter of the same at the bottom . 12 Anteroposterior diameter of same 20 Height of same vertebra to the base of the spine 63 Width across the posterior zygapophyses 66 Width across zygapophyses anteroposteriorly . 37 Genus BOLBODON Cope. Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 134. Type: Half of a skull, showing only the dermal bones of the roof. No. 4375 Am. Mus. Nat. Hist. Cope Coll. From Texas. Original description: "Molar teeth without external heel and with one median cusp. Cranial bones coossified; no grooves indicating the sutures of dermal scuta. Internal borders of the palatine bones in mutual contact, and dentigerous. "The dentition of the genus is not different from that of PhanerosauruSy as described and figured by Geinitz and Deichmiiller. In that genus, according to the authors, the cranial elements are distinct, the sutures being persistent. In Bolbodon the cranial elements are entirely coossified, excepting only the tabular bone, which is distinguishable. The nostril is large, and a turbinal bone is visible within it as in Pariotichus. The lateral and inferior bones of the brain case, and the mandible, are not preserved." Bolbodon tenuitectus Cope. (Plate 10, fig. 1.) Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 134. Type: Same as the genus. Original description: "From the middle line at the apex of the vomer to the posterior extremity of the maxillary bone there are alveoli for seventeen teeth. Of these, six only are occupied by teeth, which are Nos. 5, 7, 10, 12, 13, 16. Of these only 5, 13, and 16 have perfect crowns. The skull has been somewhat distorted by pressure, so that the longer axis of the roots and crowns are somewhat oblique to their correct positions. The roots of Nos. 5 and 7 are wide oval in section, and the long axis becomes longer posteriorly up to No. 16, in which it is a little contracted, and where the entire dimensions are smaller. The crown of No. 5 is caniniform and acute (the crown of this tooth is missing in the present condition of the specimen), is curved backwards as to its anterior face, and has a worn posterointernal face due to the opposing tooth of the inferior series. In No. 13 the crown is much more expanded transversely, and the external border is convex medially and incurved above and below. Curved shallow grooves radiate from the external (?) apex down- wards and inwards. The crown of the sixteenth tooth is cordiform, with the acute apex upwards. Shallow grooves descend from the latter. Like the maxillary teeth the palatines are widely spaced. The sections of their crowns are a wide oval placed longitudinally; apices lost. "The nostril is large and is rounded subquadrate. The orbit is large and is subround, and its border is not notched as in the Diadectes latibuccatus, nor the SYSTEMATIC REVISION 23 superior border depressed as in D. phaseoUnus. The interorbital space is gently convex, and is wider than the diameter of the eye, but how^ much wrider the state of the specimen leaves uncertain. The jugal bone is quite narrow below the orbit, its vertical diameter equalling two-fifths that of the latter. The surface of the cranium is rather minutely wrinkled, and does not display the grooves seen in the Dtadectes latibuccatus. The tabular bone forms a rounded and narrowed cap of the posterolateral angle of the skull, and is much less prominent than in the genus Chtlonyx, but more so than Dtadectes, where it is not distinguishable by suture. "Measurements. "Total length of the cranium from the pre- m Diameters of fifth tooth: M maxillary to the os tabulate inclusive . 0.284 Longitudinal 0-015 Diameters of the nostril: Anteroposterior 007 Vertical 025 Transverse 010 Transverse 033 I Diameters of the twelfth tooth : Distance from nostril to orbit 078 j Longitudinal 013 Diameters of orbit: Anteroposterior 0065 Vertical 053 Transverse 013 Tranverse 054 Diameters of the sixteenth tooth: Interorbital width (posterior to middle) .070 ' Longitudinal 010 Length of dental series (chord) .150 \ Anteroposterior 005 i Transverse 0085 "The dimensions of this skull are equal to those of Dtadectes phaseoUnus, and about one-fourth larger than those of Dtadectes latibuccatus. The bones of the cranium are thinner and lighter than those of any other species of the family that has come under my observation." Revtsed desert ption of the genus and species: The genus and species is based on a single lateral half of a skull; no other specimens are known. Closely related to Diadectes, it is distinguished by the greater thinness of the bones of the skull and the less rugose sculpture of the surface. The differences in proportions, from Diadectes, may readily be accounted for by the conditions of preservation; most of the skulls of Diadectes have been preserved more or less entire and have been subjected to pressure from above downward, the skull of Bolhodon was split in the median line before fossilization and subjected to lateral pressure. The tooth figured by Cope is the posterior one of the series and is not characteristic; in all of the species of Diadectes the posterior tooth is smaller and more simple than the more anterior ones. Genus CHILONYX Cope. Bolosaurus rapidens Cope, Proc. Am. Phil. Soc., vol. xvii, 1878, p. 507. (Also Pal. Bull. No. 29.) Chtlonyx Cope, Proc. Am. Phil. Soc., vol. xx, 1883, p. 631. Trans. Am. Phil. Soc., vol. xvii, 1892, p. 13. Proc. Am. Phil. Soc., vol. xxxiv, 1896, p. 441. Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 131. Type: An imperfect skull. No. 4357 Am. Mus. Nat. Hist. Cope Coll. From Texas. Original description: "Teeth with the long diameter of the crowns transverse to that of the jaws, and with the crown contracting to a single slightly incurved apex. Maxillary series of teeth short. Temporal fossae overroofed. Superior surface of the cranium divided into more or less swollen areas by grooves. "The single species of this genus is one of the largest saurians yet obtained in the Permian of North America." 24 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA In 1896 Cope describes Chilonyx as follows: "Teeth compressed, with an apex; no canine; os tabulate produced into a tuberosity or horn; top of head scutate." Chilonyx rapidens Cope. (Plate 10, fig. 2.) Bolotaurus rapidens Cope, Proc. Am. Phil. Soc., vol. xvil, 1878, p. 507. Chilonyx rapidens Cope, Proc. Am. Phil. Soc., vol. xx, 1883, p. 631. Type: A single tooth from the posterior or middle portion of series. No. 4356. Paratype: No. 4357 Am. Mus. Nat. Hist. Cope Coll. From Texas. Original description: "The size is many times greater than that of the species of this genus (Bolosaurus) already described, and it is uncertain whether the poste- rior tooth possesses the internal ledge characteristic of them. The anterior tooth does not possess it. The transverse diameter of the crown is considerably greater than the anteroposterior, and the convexity of the outer side is without facets. One side of the curve is flatter than the other. The enamel is perfectly smooth. The inner face is occupied by the surface of attrition of the corresponding tooth of the opposite jaw. The supposed anterior tooth is from another locality. Its section is similar to that of the present tooth, and the enamel is similarly smooth. The cutting edges are both smooth, and bounded by a little groove next the plane inner face. The crown is much more elevated than that of the tooth first described, and is in general shaped like a claw. It may be from the pterygoid bone of another genus. "Measurements. |. "Elevation of the crown (axial) o.oio Diameter of crown: Anteroposterior 006 Transverse 008" In the "Proceedings of the American Philosophical Society" for 1883, p. 631, Cope gives a characterization as follows: "The superior surface of the skull is everywhere flat, as is the external face of the maxillary. The surface of the latter is marked by moderately coarse fossae and grooves, separated by more or less fine irregular but generally longitudinal ridges. The minute sculpture of the superior cranial surface is finer and more punctate in character. The areae of this surface, already mentioned, are arranged as follows: There is a series over the orbits, which are separated from each other by straight grooves, and which grow larger and more swollen posteriorly. Between the supra- orbital rows, the areae of the top of the skull are separated by longitudinal grooves, except immediately between the orbits, where there are some narrow transverse areae. On the supraoccipital region there is a median subtriangular area, and three narrow longitudinal ones on each side of it. External to these, and on the posterior part of the squamosal region, the areae are larger and more swollen. A cluster of three of these lies between the exoccipital bone, and the smooth descend- ing surface of the posterior edge of the squamosal. Of these the one bounding the exoccipital bone is a robust cone, forming a short horn, like that occupying a similar place in the'homed toad, Phrynosoma douglassi. Between the temporal areae, and in front of the supraoccipital areae, on each side of the middle line, there are three longitudinal areae, which are successively narrower externally, the exterior being very narrow. On the frontal region, anterior to the transverse areae, are two wide longitudinal areae. Each nasal bone has a small median area, from which radiate grooves, of which some of the posterior are close together. SYSTEMATIC REVISION 25 "The occiput is excavated into a large fossa on each side of a large triangular supraoccipital region. The fossae are bounded externally by a strong exoccipital crest and at the anteroinferior corner by the 'ophisthotic' This bone projects posteriorly and downwards, in the form of a robust hook. The foramen magnum is not excavated so abruptly above the exoccipital facets as in Empedias tnolaris. "Measurements. M "Interorbital width 0.108 Length from supraoccipital crest to frontonasal suture 135 Width between apices of tuberosities of the intercalaria 113 Length from apex of tuberosities to inferior extremity of quadrate 129 Diameters of quadrate condyle: Anteroposterior 020 Transverse 039 Length of maxillary on alveolar edge 087 Diameters of base of a posterior tooth: Anteroposterior 007 Transverse 010 Diameters of base of another posterior tooth : Anteroposterior 005 Transverse 010 "A femur, which is included in the lot of specimens, has a wide head without trochanters, convex in the plane fr^^j^W^ ^' ■ of the distal condyles and flat in the direction at right angles \ (flBv "^ to it. There is a huge trochanteric fossa extending from the \i jlk > / head two-fifths the length to the condyles, bordered by a \N.^ ridge on each side. The condyles present in the same direction as the fossa posteriorly. They are separated by a deep anterior and posterior emargination. Their ante- u» . rior edges overhang the condylar articular surfaces, making » W ''•'I acute angles with them. One of the articular surfaces is smaller, is anteroposteriorly extended, and has a convex 1 1 ectad, and concave entad border. The other surface is / ■ ~^ also anteroposterior, reaching further distad, but not so far proximad as the other. Its area is greater than that of the ^fiC w^^HHo^ /i other, and it is deeply notched by the entering surface of the bone ectad and proximad. It is then contracted into a wide isthmus, and the lateral grooves which produce this k isthmus are overhung by the expansion of the anterior face. The anterior face of the femur is without ridges or ° Fig. 5. — No. 4157 Am. Mui. processes. Anterior view of right femur of Chilotiyx. xi- " Measurements. M "Length of femur 0.236 Proximal diameters of femur: Anteroposterior 047 Transverse 085 Width of shaft 052 Width distally (greatest) 115" Revised description of the genus and species: The teeth described as the type are imperfect incisors and might belong to any species of the genus Diadectes. The 26 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA genus and species rest on the paratype; they are distinguished by the larger size and the tuberculate condition of the bones of the skull. There are no lines indicat- ing the attachment of scutes as described by Cope. Genus DESMATODON Case. (Plate 8, fig. 2.) DesmaloJon hoUandi Case, Annals Camegie Museum, vol. iv, Nos. Ill and iv, 1908, p. 236. Type: A fragment of a maxillary bone with four teeth and the root of a fifth. No. 1938 Carnegie Museum. From Pitcairn, Pennsylvania. Original description: "The teeth are of peculiar interest, as they represent an intermediate stage between those of Bolhodon and those of Diadectes. They seem to indicate with little doubt the existence of a new genus which may be called Desmatodon hoUandi. The teeth are transversely elongate; the crown is slightly wider than the root and is also somewhat swollen in the anteroposterior direction. The outer half of the crown rises gently into a sharp apex, from which there is a sharp descent to the inner half, which is lower than the outer half. The inner side of the apex is nearly vertical and presents a flat face inwards; this is more prominent on the posterior and largest of the teeth than on the anterior ones. The surface of the crown is marked with fine lines and the sides of the root show the same charac- ter, but here the lines are coarser. The inner half of the crown of the anterior and the posterior teeth shows no wear, but on the two in the middle there are surfaces worn by attrition on both the inner half of the crown and on the apex. The relation of this genus to its nearest related forms is indicated in the figure here given." (See ^8- 34) .... . Revised description: This genus is closely related to the genus Diadectes, but the differences in size and character and also its geographical and geological separa- tion from the Texas beds make it advisable to regard it as distinct. Genus DIADECTOIDES nov. Diadectoides cretin sp. nov. Type: A vertebral column, nearly complete, with ilium, femur, tibia and fibula, and fragments of the skull. No. 650 University of Chicago. From Willbarger County, Texas. This skeleton resembles that of Diadectes in many respects and might at first be considered as a young individual of that genus, but the proportions of the limbs, the shape of the apices of the spines, and the free neural arch indicate a distinct genus. The bones are covered with a hard matrix which permits the general form to be made out, but conceals minor details. It was only after considerable study that it was possible to be certain of the presence of hyposphene and hypantrum. ■^i^Fig. 6 is after an original by Dr. Williston, who most kindly turned the specimen over to me after having begun work upon it. The single sacral vertebra is the sixteenth of the series preserved; it is certain that the number of presacrals is incomplete, probably four or five are wanting. The dorsal vertebra are, as in Diadectes, very similar throughout the series. The spines are short and low, but instead of terminating in rugosities as in Diadectes, they terminate in flat oval surfaces. The sides of the neural arch are swollen and convex, as in Diadectes. The zygapophyses are horizontal; the neural arches are wider than long, and the zygapophyses overlap so far as to bring the spines in con- tact. The result is a short, heavy, vertebral column with very little possibility of lateral motion. Hyposphene and hypantrum appear to have been present but are obscured by the matrix at most places. The neural arches fit so closely upon each SYSTEMATIC REVISION 27 other that the hyposphene-hypantrum articulation can not be seen from the side, as in Diadectes. The transverse processes are similar to those of Diadectes, having single faces inclined downward and forward to the upper edge of the centrum. The neural arches are free from the centra, which are detached in most parts of the column. The lower edges of the neural arches are rounded and appear to have been attached to the centrum by a considerable mass of cartilage. The centra are deeply biconcave or notochordal; the lower surface can not be clearly made out, but there seems to have been a broad, low median keel. No intercentra can be made out, but small ones were undoubtedly present. Fio. 6. — Outlinf of part of vertebral column of DituUcioiJes crttin. x J. Uniy. of Chicago. The sacral vertebra resembles the others in the neural arch and spine, except that the posterior zygapophyses are reduced in size and this portion of the neural arch is thinner. The transverse process, however, presents a very large face almost directly downward, for the head of the sacral rib. The centrum is not attached to that of the following vertebrae; there is no sacrum. Posterior to the sacral vertebra there are fourteen caudal vertebm. The apices of the spines of the first are more elongate oval and they rapidly decrease in size. The transverse processes do not have elongate faces slanting forward and downward, but round, rather large faces looking outward but largely downward. Chevrons appear on the fourth or fifth; these are short, bifurcate above, and inclined to the rear. The neural arches and centra are narrower in this region and the whole tail was flat and high. The ribs are single-headed, long, and slightly curved; free ribs occur on all the presacral vertebrae preserved; there were no true lumbars. The sacral rib is very short and heavy; the proximal end was attached by two wide faces to the transverse process and the centrum; there is practically no shaft and the distal end is expanded into an elongate oval, with its main axis vertical, applied to the inner side of the ilium. The first caudal ribs were free, but they soon disappear. The ilium is short and stout with a slightly convex anterior edge and a promi- nent posterior projection. A good-sized process overhangs the acetabulum. The attachment of ischum and pubis was sutural. Tht femur is exceptionally short and strong. The upper end presents a nearly flat articular face; there is a prominent process on the posterior face near the anterior 3 28 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA end, in the position of the concavity of most reptilian forms. This is most striking and leads to some doubt as to the correct identification of the bone; it resembles the tibia of other forms, but is far too large to be a tibia of this creature, and as both bones are present and show this character, its determination seems certain. The shaft is short and thick, the lower end is imperfectly divided into two faces. The tibia is similar in form to that of Diadectes and resembles quite closely the femur in general form. The lower end has two distinct faces at an angle of 45°. T\\t fibula is probably represented by the two ends; little can be made out be- yond its exceptional heavy form. Fragments of the skull with some poorly preserved teeth show that the skull was in general form like Diadectes. Measurements. mm Length of the series of vertebrse 380 Length to posterior end of sacral vertebra 230 Length of ilium on midline 54 Length of femur 47 Width of distal end of femur 37 Length of tibia 36 Length of a mid dorsal rib 127 Length of an anterior chevron 24 This creature seems to have carried the peculiarities oi Diadectes to an extreme. The vertebral column is more closely knit and even shorter. The limb bones are heavy and very short. The tail was moderately long, but very thin and fairly high. The whole appearance must have been that of a short, low, and very wide creature with broad stumpy legs. The evident great strength, coupled with the essential weakness of the free neural spines, leads to the suggestion that the specimen is that of an immature animal. Family BOLOSAURIDAE Cope. Qjpe, Proc. Am. Phil. Soc., vol. xvn, 1878, p. 529. Case, Bull. Am. Mus. Nat. Hist., vol. xxiii, 1907, p. 652. Original description: "Bolosaurus will form the type of another family charac- terized by the transverse position of the crowns of the teeth, under the name Bolo- saurida." Revised description (Case, 1907): "Small Cotylosaurians with the cheek teeth elongate transversely and with a prominent cusp, in the upper series on the outer edge and in the lower series on the inner edge; the cusps showing slight wear in mature specimens. The family is distinguished from the Partottchtdcs hy the pres- ence of the cusps on the teeth and by the presence of but a single row in the lower jaw, and from the Diadectida by the presence of an elongate parasphenoid rostrum and a prominent outer process of the pterygoid bearing a row of teeth on the lower edge." Revised description: 1. Skull smooth or slightly rugose. 2. Pineal foramen small. 3. Occipital condyle rounded. 4. No armor. 5. Ribs not expanded. 6. Body low; limbs short, not heavy. 7. Not determinable. SYSTEMATIC REVISION 29 Genus BOLOSAURUS Cope. Bolosaurus Cope, Proc. Am. Phil. Soc., vol. xvii, 1878, pp. 506 and 529. Type: An imperfect posterior portion of a skull. No. 4320 Am. Mus. Nat. Hist. Cope Coll. From Texas. Original description: "Teeth fixed in shallow alveoli, and with the crowns expanded transversely to the axis of the jaws. The crowns swollen at the base, and with low apex, divided vertically into two equal portions. The posterointernal half in the maxillary series is low and horizontal; the anteroexternal portion forms a low cusp, which has a semicircular section. The teeth of the lower jaw are similar, but the relative positions of the ledge and cusp are reversed. Anterior teeth of superior series composed of external cusp and internal ledge. No enlarged canine or incisor teeth. Bones of face not sculptured." Revised description: This is contained in the revised description of the family. Bolosaurus striatus Cope. (Plate 7, figs. 4, 5, 6) Bolosaurus striatus Cope, Proc. Am. Phil. Soc., vol. xvii, 1878, p. 506. Bolosaurus striatus Case, Bull. Am. Mus. Nat. Hist., vol. XXIII, 1907, p. 653. Type: Same as that of the genus. Original description: "Char. Specif. The external surface of the crown is marked to the apex with waved grooves of the enamel. The edge of the elevated cusp, which presents posteriorly in the maxillary teeth, constitutes the abrupt ter- mination of the exterior face, and is serrate by the interference of the sulci. The edge of the basal ledge is slightly serrate. The muzzle is rather elongate, and the sides of the maxillary and dentary bones are plane and smooth. The mandible is rather narrow, and forms a narrow wedge in the profile outline. It rises posteriorly behind the dental line. The teeth are separated by intervals as wide as a tooth. "Measurements, "Long diameter of orbit No. I 0.0130 Depth of upper jaw at orbit OO45 Depth of lower jaw at front of orbit 0050 Four teeth in 0080 Elevation of a crown 0025 Transverse diameter of molar number 2 0025" The foregoing description, by Cope, was evidently taken in large part from the type skull, but some portions of the description are evidently taken from a second skull. No. 4321 Am. Mus. Nat. Hist. Cope Coll., and perhaps from other specimens. He adds: "A slight modification of the character is found in two imperfect crania. The principal character is to be seen in the teeth. The enamel of the ex- ternal surface of the cusps is not sulcate, but is smooth; and the posterior cutting edge of the cusp is much less distinct. It is, in fact, obtuse and not serrate. The orbit is large, and the front and muzzle are regularly decurved to the premaxillary border. The angle of the mandible is moderately prominent, and is massive and obtusely truncate. The interorbital region is flat in the transverse direction. "Measurements. „ "Length of the skull to the mandibular angle 0.050 Length of the skull to the orbit 015 Long diameter of the orbit .0l8 Width of the interorbital region 009 Sixteeth in .010** Revised description: This is contained in the revised description of the family. 30 A REVISION or THE COTYLOSAURIA OF NORTH AMERICA Family NOTHODONTIDAE Marsh. This family was established without diagnosis. Genus NOTHODON Marsh. Am. Journ. Sc, vol. xx (3), 1899, p. 410. Type: A portion of the skull and some limb bones. Yale University Mus. From New Me.xico. Original description: "These reptiles may be readily distinguished by the dentition. In each premaxillary there are two slender pointed teeth. In front of the maxillary J^"^ a\ y-^^— \ there are one or two similar teeth, followed by a C / C J L. .J number with narrow transverse crowns, resem- '^ '* \ \ f "1 bling in form the premolars of some carnivorous a 6 jQ mammals. These crowns, when unworn, have a central cusp, and on each side a tubercle, some- . ^ ^^ itsf^ll what like the premolars of the genus Canis. In d the present species the first and last of the teeth y.^—,- ^ :-..- - . — ^ ,. are smaller than the middle ones. The limbs / lllj were short, the long bones had their extremities " * ' covered with cartilage, but the carpals and tarsals were well ossified. The centra were deeply con- ravp anrl fVip fail was Inner ric.T.—a,b,c,thret Mtho( NoiltoJon Itnlus. cave ana tne taU was long. YJeUniv.Mus. in proof, ai be wai unaware that I had uaed k in the manutcript. — E. C. C. SYSTEMATIC REVISION 51 aguti, but there is a slighter development of the same thing. The posterior portion of the pterygoid takes part in the border of the palatal vacuity, forms a part of the border of the auditory notch, and aids in the closure of the posterior portion of the skull. Numerous small teeth are found on the anterior process of the pterygoid and on the external process. "The foramen magnum is bordered by four bones: (i) Exoccipital; (2 and 3) the inner branches of the exoccipitals which expand broadly and unite above with the (4) supraoccipital. The outer branches of the exoccipitals bend first outward and then upward to the tabulare, inclosing a foramen between them and the tabu- late. Above the foramen the border Hne between the two inner branches of the exoccipital are not so clear; it almost seems as if they inclosed between them and the supraoccipital another foramen. The lower jaws are closely pressed against the skull in both specimens. No observations can be made on the teeth. "Measurements of skull. ' cm "Breadth of the skull on the posterior border 10.5 Total length in the mid (so far as preserved) 10.2 Separation of the orbit from the posterior border of the skull (auditory notch) 1 .8 Distance between orbits 3.1 Length of orbit ca.2.7 Breadth of orbit ca.2.6 "Pectoral Girdle: The interclavicle is rhombic anteriorly with a long posterior process. The anterior end has a rough radiate sculpture. The clavicles are wing- like, the posterior end bends backwards and upwards in an obtuse angle to form spatulate process so that they covered in this way the sides of the animal. The proximal ends do not meet in the median line and are covered with rough sculpture. There is no evidence of a cleithrum; the condition of the specimens does not permit a final conclusion as to its presence. The vertebras shown have low transverse process, the neural arch is saddle-shaped and broader than long. The pre- and post-zygapophyses are horizontal. The ribs are double headed ( .?) and the distal end is expanded and shovel-shaped." Revised description of the genus and species: 1. The skull a little broader than long; blunt anteriorly. 2. Orbits large, more in the posterior half of the skull than in the middle, looking laterally. 3. Not determinable. 4. Not determinable. 5. Not determinable. 6. Basioccipital and basisphenoid not large. 7. Supraoccipital plates, nearly vertical but occupying a considerable space, are on the upper surface of the skull. 8. Skull with definite reticulate sculpture. 9. Not determinable. 10. Cleithrum absent. 11. Not determinable. This genus was reported by Broili to have both prosquamosal, squamosal, and quadratojugal bones, but a reexamination of the specimen by Dr. Broili and the author shows that there are but two bones on the side of the skull, as in the Pario- tichidee and Captorhinidce. The presence of an intertemporal bone justifies its separation as a distinct family. (See also Williston, Journal of Geology, vol. xix, P- 232.) 52 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA Genus CONODECTES Cope. Cope, Am. Nat., vol. xxx, 1896, p. 398. Cope, Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 129. Type: An imperfect skull. No. 4342 Am. Mus. Nat. Hist. Cope Coll. From Texas. Original description: In the "American Naturalist" for 1896 Cope gave an analysis of the family Otoccelida: "Cranial roof excavated laterally behind, forming a large meatus auditorius. Teeth present in a single row, not transversely expanded. Suspensorium directed posteriorly; nostrils vertical." In the "Proceedings of the American Philosophical Society" he writes: "Quadrate bone extending posteriorly so that the mandibular articulation^ is opposite the posterior border of the cranial table. Meatus auditorius small, con- nected with the meatal notch. Nostrils directed upwards and a little outwards. Teeth conic, acute, increasing in size to the middle of the maxillary region." Conodectes favosus Cope. Proc. Am. Phil. Soc., vol. xxxv, 1896, p. 129. Original description: "The teeth preserved show that the premaxillary teeth are small, as in the Isodectes megalops, and that they increase in length posteriorly. The maxillopalatines are excavated on the median line, so as to present two parallel ridges which continue as far as the posterior border of the internal^nares. These ridges probably continue on a palatine bone and they support each a tooth near the posterior extremity. In Isodectes megalops the palatines support numerous small teeth on their inner borders. I find no trace of the interior rows of maxillary and mandibular teeth which are characteristic of the Fariotichidee. Some such teeth may, however, have existed, as a portion of the maxillary bone is wanting from both sides of the skull. "This species is seven or eight times the linear dimensions of the Isodectes megalops, and a little smaller than the Otocaelous testudineus. The skull is as wide posteriorly as it is long, and is rather depressed, so that the orbits and nares have a vertical as well as a lateral presentation. The muzzle is flat and projects beyond the lower jaw, and it is rounded in outline, and not narrowed and pro- tuberant as in most of the species oi Pariotichus. The internareal and interorbital regions are flat. ^The narrower brain case is continued between the orbits, and its lateral walls are robust. The palatine bones extend from the maxillaries, and approximate each other nearly on the median line, where they are separated medially by a groove, which becomes wider posteriorly. No teeth can be discerned in the specimen, excepting the large anterior one already mentioned. The surface of the bone is, however, not in good condition. The plate of the pterygoid extends to the jugal on each side, and its posterior border is but little deflected, and is at right angles to the long axis of the skull with indications of teeth. The posterior branch of the pterygoid is slender. The occipital region is injured. The superior surface of the skull is sculptured, on the posterior frontal region in a coarse honeycomb pattern, the ridges occasionally forming small tubercles. "The teeth are conic, acute, and with a round section. In this respect they differ from those of most of the species oi Pariotichus, where the crowns are obtuse. They are rather closely placed, and they increase in length to below the anterior border of the orbit. Their character posterior to this point can not be ascertained. The single, large palatine tooth is similar to the maxillaries in form, and equals in dimensions the maxillary tooth which is below the posterior border of the nostril. SYSTEMATIC REVISION 53 The posterior border of the internal nostril marks a point half-way between the posterior border of the anterior nostril and the anterior border of the orbit. "Measurements. nim "Total length of skull . 158 Width posteriorly 152 Width between nostrils 20 Length from end of muzzle to posterior border of pterygoid plate 103 Width between summits of ridges of vomer 10 Length from posterior border of nostril to anterior border of orbit 41 Lengthof longest maxillary tooth . 10 Diameter of longest maxillary tooth at base 3.5" Revised description: The original description is correct except with regard to the palate. The paired prevomers are plate-like and close the anterior portion of the palate; following these are distinct palatine and pterygoid bones, the latter coming close together in the median line. Conodectes may, as suggested by Williston, be identical with Seymouria. FOREIGN FORMS. Genus PAREIASAURUS Owen. Owen, Cat. Foss. Rep. South Africa, 1876, p. 9. Seeley, Phil. Trans. Roy. Soc., 1888, p. 75. Broom, Annals South African Museum, vol. iv, 1903, p. 123. Bull. Am. Mus. Nat. History, vol. xxviii, art. xx, 1910, p. 201. Broom in his last paper gives the following summary oi Pareiasaurus: "Though four fairly good skeletons of Pareiasaurus have heen discovered which reveal most of the general structure of the skeleton there are many details of which we are still ignorant. "The skull is large with the temporal fossae completely roofed over, but the detailed structure of the roof is still doubtful. There appears, however, to be littlt i Fio. 13 — Palate of Pareiasaurus. After Broom. Slightly restored. doubt that there is a quadratojugal. The bones are pitted somewhat like those of Stegocephalians. There is a distinct septomaxillary. The palate is fairly well known and, as shown in the figure (fig. 13), has the typical structure met with in most primitive reptiles. There are paired prevomers bearing teeth, paired palatines 54 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA probably also bearing teeth, and apparently small transpalatines. The pterygoids are fairly large and have rows of small teeth. "The occipital condyle is flat. "The vertebrae are large and massive and have intercentra. The zygapophyses are veiy broad. The ribs for the most part are single-headed. "The shoulder girdle has a large scapula with a well-developed acromion, large precoracoid and fairly large coracoid. There is well-developed cleithrum, fairly large clavicles, and a massive T-shaped interclavicle. "The humerus is very massive and has a large deltopectoral ridge. The ulna has an olecranon process. "The carpus, so far as known, appears to be similar to that of most early reptiles. "The digital formula is unknown. It has been stated to be 2, 3, 3, 4, 3, but in the closely allied Propappus it is most probably 2, 3, 4, 5, 3, two digits having certairily more than 3 phalanges. "There are apparently no abdominal ribs. "The pelvis is remarkable for having the ilium large and directed forward as in Mammals and the higher Therapsida. "The teeth are pecularily specialized. Externally they are markedly convex, the inner side being nearly flat. Round the edges are 7 or 9 large cusps arranged in a semicircle." Genus ANTHODON Owen. Owen, Cat. Foss. Rep. South Africa, 1876, p. 14. Imperfectly known. Skull more vaulted than in Pareiasaurus. Teeth with short, compressed, and anteroposteriorly expanded crowns, having a convex, sub- trenchant free edge, marked by numerous crenulations, roots long and narrower than the crowns. Centra of the dorsal vertebrae with deeply cupped terminal faces, and no evidence of the presence of intercentra. Genus PROPAPPUS Seeley. Seeley, Proc. Roy. Soc, vol. XLiv, No. 267, 1890. Broom, Annals of the South African Museum, vol. iv, pt. vui, 1890, p. 351. Type: A humerus. No. 36250 in the British Museum. Homotype: The "greater part of a large skeleton," now in the South African Museum. Described by Broom. Description of the homotype: Skull represented by fragments of a maxilla and the mandibles. Mandibles with two projections from the lower edge, instead of one as in Pareiasaurus. The crowns of the teeth flattened, semicircular, with eleven cusps on the maxillary teeth; cusps on the mandibular teeth similar to those on the maxillary but smaller. Vertebrae as in Pareiasaurus, the centrum rather slender and elongate; biconcave but not deeply excavated. Intercentra present. Transverse process broad and powerful, spine low and short. Limb bones and girdles differing little from Pareiasaurus. Tarsus with a single proximal element; distal tarsals probably small and largely cartilaginous. Foot broad and short, digital formula almost certainly 2, 3, 4, 5, 4, certainly more than 2, 3, 3, 4, 3. "Whole back and probably sides covered with a carapace of bony plates somewhat after the manner of a crocodile." There is no evidence of any plastron. Genus ELGINIA Newton. Tran». Roy. Phil. Soc., vol. 184, pp. 43'-503. Type: The cast of a skull from the Elgin Sandstone. Preserved in the Museum of Practical Geology, London. SYSTEMATIC REVISION 55 This genus is known only from the cast of a cavity in the sandstone and so only the external form can be made out. It is evidently closely related to Pareia- saurus, but has numerous prominent spines on the posterior edge of the skull, resembling in this regard the Pareiasaurians from Northern Russia. Genus SCLEROSAURUS H. v. Meyer. Sclerosaurus H. v. Meyer, Paleontographica, Bd. vii, pp. 35-40, Taf. 6. LahyrinthoJon Wiedersheim, Abh. Schweiz. pal. Gesell. Bd. 5. Aristodesmus Seeley, Proc. Roy. Soc., vol. 59, pp. 167-169. Aristodesmus Seeley, Quart. Journ. Geol. Soc., vol. 56, pp. 620-645. Sclerosaurus v. Huene, Geol. u. pal. Abltndlg. n. b., Bd. VI, Heft I. The specimen was found in the Buntersandstein near Rheinfelden. Skull completely roofed over and the posterior bones carrying prominent spines, especially the squamosal, quadrate, and quadratojugal. Skull flatter than that of Elginia. Occipital condyle hemispherical, as in Pareiasaurus and Elginia. Von Huene figures large palatal vacuities in his reconstruction of the palate, but there seems no warrant for this in the specimen or from analogy with other Pareiasaurians. External nares, terminal and vertical. Seven blunt conical teeth preserved in the maxillary and four rather sharper ones in the premaxillary, but it is not certain that \ Fio. 14. — Outline reconttruction of Sclerosaurui. After von Huene. this is the complete number. Surface of the skull smooth with the exception of the projections at the back of the skull. Seeley and Wiedersheim report twenty-two presacral vertebrae, v. Huene twenty-one. Vertebrae notochordal and shorter on the lower line than the upper, leaving spaces for intercentra; a sharp keel on the lower surface of the centrum gives it a triangular section. Neural spines short, with the upper ends expanded and rugose where they came in contact with the dorsal plates. Transverse processes strong and heavy with single articular faces for the single-headed rib. Three sacral vertebrae, the ribs of the anterior and pos- terior being larger than the middle one. Shoulder girdle with free scapula, cora- coid and precoracoid, cleithrum probably present. Carpus with two rows of bones, a proximal, consisting of radiale and ulnare, and a distal with four elements. In the pelvis the pubis and ischium meet each other at an angle and resemble more the same bones in Pareiasaurus than in the Diadectidce and CaptorhtnidcB; the ilium resembles that of Dicynodon. Astragalus and calcaneum united in a single large element, the distal row not ossified. Dorsal armor consisting of six rows, the inner two rows lying on either side of the neural spine and overlapping the postzyga- pophyses; each with a dorsal keel and a pitted sculpture. Outer rows of smaller irregular plates. 56 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA Genus PHANEROSAURUS H. v. Meyer. Phanerosaurus naumanni, Paleontographica, i860, Bd. vn, pp. 248-252, Taf. xxvii. H. V. Meyer described a specimen consisting of four pos- — t A r A Fig. 17. — Outline of Tf/er/K/on. After Boulenger rauia 2,3,4, 5, 4. ^^ restorationi b, lateral view of dtuU. Suborder PANTYLOSAURIA nov. 1. Skull completely over-roofed. 2. Quadrate covered or exposed, without a posterior hook forming a notch for the external meatus. 3. Prosquamosal present. 4. External process of the pterygoid present and covered with numerous small teeth. 5. Parasphenoid rostrum appearing on the lower surface of the skull. 6. Ectopterygoid absent. 7. Tabulate present. 8. Cheek teeth simple, conical; one or more than one row in each jaw. 9. 10, II, and 12. Not determinable. Family PANTYLIDAE nov. Only the skull known. 1. Slightly larger than the Captorhinida. Skull cordiform. Quadrate not exposed. Surface with a particularly close, reticulate sculpture. 2. Median incisors very slightly larger than the others. Cheek teeth in the form of blunt, swollen cones; the second or third larger than the others. Posterior cheek teeth small. 3. More than one row of teeth in the jaws. SYSTEMATIC REVISION 59 Genus PANTYLUS Cope. Bull. U. S. Geol. Survey of the Terrs., vol. vi, art. ii, 1881, p. 79. Trans. Am. Phil. Soc., vol. xvii, 1892, p. 14. Type: A skull. No. 4330 Am. Mus. Nat. Hist. Cope Coll. From Texas. Original description: "The superficial ossification is complete, leaving only nostrils, orbits, and parietal fontanelle. Surface sculptured. Mandible with an angular process. Teeth shortly conic, obtuse, and without grooves or inflections, increasing in size toward the anterior part of the jaws. Mandible supporting several rows of teeth which oppose a pavement of obtuse teeth on the palate. These are situated on either the palatine or anterior part of the pterygoid bones. Quad- ratojugal and malar bones well developed. No lyra or mucous grooves." The genus was regarded as Stegocephalian in character, but in the next year was placed among the Reptilia (26). In 1892 Cope mentions that Pantylus agrees with Chilonyx in the composition of the cranial root, except that the suspensorium is vertical and not directed forward. Revised description: 1. Skull flat on top with the sides steeply inclined; the posterior surface nearly vertical. 2. Orbits of medium size, near the middle of the skull. 3. Teeth, blunt, swollen cones. 4. Maxillary teeth nearly uniform in size except the second or third, which is larger. 5. Teeth in more than one row in lower jaw and probably in the upper also. 6. Not determinable. 7. Supraoccipital plate vertical. 8. Skull with close reticulate sculpture. 9. 10, II. Not determinable. Pantylus cordatus Cope. Bull. Geol. and Geog. Survey of the Terrs., vol. vi, art. n, 1881, p. 79. Trans. Am. Phil. Soc, vol. xvii, 1892, p. 25. Type: Same as the genus. Original description: "The skull of the Pantylus cordatus is about as large as that of the fully grown snapping tortoise, Chelydra serpentina, and has somewhat the same form of outline. The vertex is flat; the postorbital region is swollen, and the muzzle is abruptly acuminate. The orbits are lateral with a slight vertical exposure, and are widely separated. The front is deflected from opposite their posterior margins, and the muzzle protrudes considerably beyond the lower jaw. The premaxillary bones form a triangle whose apex does not appear on the superior surface of the muzzle, and the nares are rather close together, and lateral in their vertical presentation. The upper extremity of the snout is occupied by the large nasal bones, which are followed by the larger frontals. The lachiymal and pre- frontal are both well developed, the latter extending backwards to meet the post- frontal near the superior border of the orbit. The posterior border of the skull is damaged, but enough remains to show that it was concave. The symphysis mandibuli is short. The rami are wide, and are flat below the inferior surface, forming a rounded angle with the interior surface. The angular process is in line with the external border of the ramus. "The sculpture of the cranium proper is strong, consisting of pits separated by strong narrow ridges, forming a honeycomb pattern. The fossae are smaller on 5 60 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA the buccal regions. On the anterior part of the mandible the fossae are distinct; on the median and posterior part the ridges become linear. A narrow triangular space on the external side posteriorly, with its long apex on the inferior margin, is smooth. "There are two subequal obtuse teeth, on the border of each premaxillary bone. I can not count the number on the maxillary, but there are four anterior to the line of the anterior border of the orbit. Of these the next to the anterior one is larger than the rest, though of the same shortly conic, obtuse form. These teeth are rather large for the size of the skull. At a point near the middle of the ramus of the mandible, where it is broken off, there may be counted five teeth in a transverse series. Of these the second from the external border is the largest, and has a regularly rounded crown. Six teeth may be counted on a transverse fracture of the palatine bone. Of these the four external have obtusely rounded crowns, and the third from the external border is the largest. The crowns of all the teeth are hollow. "Measurements. "Length of cranium to transverse line connecting the posterior borders of the m quadrates o.o'jj Width between the same points . 082 Length of axis of cranium to Hne connecting the anterior borders of the orbits . .018 Interorbital width 032 Longitudinal diameter of the orbit 016 Length from orbit to nostril 015 Projection of muzzle beyond mandible 010 Length of alveolar edge of premaxillary . .007 Height of crown of large maxillary tooth 0045 Fore and aft diameter of maxillary 0035 Width of mandibular ramus below at middle 020" Revised descrtptton: This is contained in the revised description of the genus. Pantylus coicodus Cope. Proc. Am. Phil. Soc, vol. xxxiv, 1896, p. 450. Type: An injured anterior half of a cranium. No. 4330 Am. Mus. Nat. Hist. Cope Coll. From Texas. Original description: "The right dental series includes , ■'"'wylv 1 eleven teeth, which are of subequal dimensions. The crowns are robust and somewhat swollen at the middle, and with a I /v small median subacute apex. The matrix covering the palate ) rf is rather hard, and in removing it only three internal teeth were detected. Two of these are near the maxillaries, and F.,.,8._s„c»imaxiUaryt«th just within the last and the penultimate respectively. The oi PantyUs cokodus. xi. No. third is opposite the antepenultimate maxillary and is as far U'l^^^^^^fl^::^ interior to it as the length of the last three maxillaries. This tmitic form. xf. No. 4336 and the posterior palatine teeth are as large as the maxillaries, '^'"' '^"'" the other is smaller. The crowns have the same form as those of the maxillary series. "This species is of about the dimensions of the P. cordatus, but the palatine teeth are less closely placed. The inequality in size of the maxillary teeth characteristic of the P. cordatus is not seen in the P. coicodus, and the form of the crown in the two species is distinct. Those of the P. cordatus are obtuse, and without the little apex of the new species. In the latter the dental crowns have nearly the form of the seeds of grass, Coix lachryma. "Accompanying the specimen above described is a fragment of apparently a dentary bone, which supports eight teeth and parts of teeth. The crowns stand SYSTEMATIC REVISION 61 on shanks which rise above the parapet of the jaw, but have a deeper attachment on the inner side, being thus partially pleurodont. The crowns are swollen at the base as in the maxillary teeth, but the apices are more produced, being regularly conic. The apices are all lost. The teeth belong to a rather larger animal than the one described above, and perhaps to another species. "Measurements. "Length of a series of eleven maxillary teeth 0-037 Diameters of the crown of a maxillary tooth: Longitudinal 004 Transverse 003 Distance from ninth tooth to anterior palatine 006" Revised description: The specimen shows a row of cheek teeth in a fragment of a badly crushed skull, and several loose teeth in the matrix. It is impossible to tell whether the teeth described by Cope are in position or not. The only charac- ter by which these teeth can be distinguished from those of P. cordatus is that the apices are drawn out sharply into a fine point. This point would very quickly be worn away and leave the characteristic blunt cone of P. cordatus; it is very possible that the presence or absence of the sharp points is but a character of age. The species is very doubtful. INCERTAE SEDIS. Genus DESMOSPONDYLUS Wiiliston. (Plate 11, figs. 4, 5.) Desmospondylus anomalus Wiiliston. Case, Joum. Geol. vol. vii, p. 718, pi. in, figs. 4a and 4b. Wiiliston, Bull. Am. Geol. Soc., vol. xxi, 1910, p. 280. Type: A humerus. No. 6541 University of Chicago. From Vermilion County, Illinois. This specimen was recognized by Case in 1900 as reptilian in character and probably cotylosaurian. Its publication was reserved for this volume. The dis- covery of additional material by Wiiliston permitted him to give a more complete description, which is quoted below: "The vertebrae, of which there are 20 or more centra and fragmentary arches, in addition to the connected series of 7 or 8, present some extraordinary char- acters— characters which are very suggestive of amphibian affinities, annectant between the rhachitomous and holospondylous types. The centra, coming all of them apparently from the posterior dorsal region and the tail, are short, almost disk- like, deeply concave, with a small perforating foramen. The arches are entirely free; the sutural surface for their attachment is extensive, situated on the anterior three-fourths of the centrum and extending downward on the front margin to below the middle. Back of this sutural surface there is a similar beveled surface extending about one-fourth of the length of the centrum, which also reaches down on the posterior side to the middle of the centrum. The arches are very low, with a rudi- mentary spine only, resembling the arches of Labidosaurus or Captorhinus. The zygapophyses are very large and broad, with their surfaces nearly horizontal. Below and back of the anterior zygapophyses there is, on either side, a distinct diapophysis, on the more anterior vertebrae standing out prominently, on the poster- ior ones a mere rugosity. Lying by the sides of these processes were a number of small ribs, which seem to have been single-headed, inasmuch as no double-headed ribs were found in the matrix. However, as Labidosaurus has quite this form of 62 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA diap>ophyses posteriorly with double-headed ribs, it is not impossible that such was the character of the ribs on this genus. "The anterior border of the pedicel, beginning low down, projects forward, so that if two vertebrae were closely applied the arch would rest on two centra, though chiefly on the posterior one, and, so far as I can determine from careful measure- ments, this would be the case with the zygapophyses closely interlocked. "That this was not the condition ordinarily, however, is rendered certain by the presence of extraordinarily large intercentra found in position between several of the centra. Relatively, as compared with the centra, these intercentra are the largest known in any vertebrate, suggesting impressively the lower half of the pleurocentra of Cricotus. When in position they reach upward to the middle of the centrum, and almost or quite touch the extremities of the arch. If the ribs were double-headed the capitulum must have articulated with the upper ends of the intercentra. These intercentra are narrower above, so that there is left a dis- tinct free space between the upper parts of the adjacent centra in the horizontal straight position of the column. When curved upward, however, the arches would fill the interstice between the contiguous vertebrae, leaving a wedge-shaped space below, filled with the intercentrum. Some of the centra preserved are hardly more than half the diameter of the largest. They are evidently caudal vertebrae, though no indications of chevrons have been discovered. Others are even more disk-like than the ones figured, resembling so closely various centra attributed to Cricotus from the Illinois deposits, that it is probable that they really belong in this genus and are centra, rather than to Cricotus, especially so as they agree in size with the femur mentioned above. "Not only are the vertebrae so curiously intermediate between the ordinary reptilian type and the embolomerous type, but the limb bones, both humeri and femora, were referred unhesitatingly to the amphibians before the vertebrae were recognized. The humerus is extraordinarily stout and rugose for its length. Immediately below the lateral process there is a stout process, hitherto characteristic of certain temnospondylous amphibians, which I have called the ectepicondylar pro- cess, most characteristically seen in Eryops and Euchirosaurus. No such process is known in any Permian reptile, certainly in no Cotylosaurian. Furthermore, the median process is developed into a stout protuberance, quite as in Eryops. On the other hand, there is an entepicondylar foramen, remarkable for its large size, known only among amphibians in Diplocaulus and Cochleosaurus, wholly unrelated forms. "The femur also is remarkably amphibian in character in the extraordinary development of the adductor crest, a character known in no other Permian reptile. The digital fossa is extraordinary for its extent and depth, reaching nearly to the middle of the bone. The bones identified as tibia and radius (the former was found close to the femur and ilium, the latter in the wash) present no peculiar char- acters, though remarkably stout and robust. "Among the material in the wash are fragments of a small skull mingled with Trimerorhachis skull material, but there is too much doubt of their reptilian charac- ter to make it worth while describing them'until further evidence of their identity is forthcoming. "That the present genus is not a pelycosaurian is, of course, evident; its rela- tionships with the cotylosaurians are more apparent. Nevertheless, the great differences in the structure of both vertebrae and limb bones from anything known among either the diadectid or pariotichid types render the exact position of the genus very doubtful. Possibly, as I have said, it may eventually turn out to be congeneric with some one of the few forms in which the vertebrae and limb bones are yet unknown, especially Pantylus." SYSTEMATIC REVISION 63 COMPARATIVE TABLES. Table I. — Showing the Characters of the Order Cotylosauria. CHARACTERS COMMON TO THE PRIMITIVE REPTILES. 1. Vertebrae notochordal or deeply amphicoelous. 2. Intercentra present. 3. Entepicondylar foramen present (except in most primitive forms Eosauravus (?) and Sauravus). 4. Ischium and pubis flat and plate-like. 5. Five elements in the distal row of the tarsus (when ossified). 6. Abdominal ribs present ( ? ). CHARACTERS DISTINCTIVE OF THE COTYLOSAURIA. 1. No openings in temporal portion of the skull. 2. Neural arches of the vertebrse broad and low; sides of arches swollen; neural spine low and stout. 3. Teeth tending to become elongate transversely to the axis of the jaw and to become tuberculate. 4. Herbivorous. 5. Body relatively short and low. The limb bones decidedly short and strong with powerful muscular attachment. 6. Neck so short as to be practically absent. 7. Ribs single-headed. , _,. , Table II. — Contrasting the Suborders of the Cotylosauria. I. Diadectosauna. * ' ^ 1. Quadrate and external auditory opening exposed by the cutting away of the posterior edge of the roof of the skull. 2. Upper end of the quadrate bent backward and downward in a hook. External face of the quadrate concave and forming a funnel with its apex at notch formed by hook mentioned. 3. Temporal region covered by two bones, the squamosal and prosquamosal. 4. External process of the pterygoid absent or poorly developed; edentulous. 5. Parasphenoid rostrum not appearing on the lower surface of the skull between the pterygoids. 6. Ectopterygoids rudimentary or absent. 7. Tabulate absent or doubtfully present. 8. Cheek teeth expanded transversely to the axis of the jaw. A single row of teeth in each jaw. 9. Hyposphene-hypantrum articulation present. 10. Coracoid and procoracoid united with the scapula. Cleithrum present. 11. Ischium and pubis broad and plate-like. 12. Abdominal ribs absent (?), not observed in any specimen. II. Paretasauria. 1. Skull completely overroofed. Quadrate concealed. 2. Quadrate without the hook marking the opening of external meatus. 3. Temporal region covered by two bones, the squamosal and prosquamosal (quadratojugal). 4. External process of the pterygoid present (indeterminable in Pareiasaurus), with numerous small teeth. 5. Parasphenoid rostrum appears on the lower surface of the skull between the pterygoids. 6. Ectopterygoid present. 7. Tabulate present, often small. 8. Cheek teeth obtusely conical, one or more than one row in the jaws. Tuberculate or simple. 9. Hyposphene-hypantrum articulation absent. 10. Coracoid and procoracoid united with scapula (free in Pareiasaurus). 11. Ischium and pubis broad and plate-like; horizontal or the two sides meeting at an angle. 12. Abdominal ribs present or absent (?). III. Pantylosauria. 1. Temporal region completely overroofed. 2. Quadrate covered or exposed; without a posterior hook forming an external meatus. 3. Temporal region covered by three bones, the squamosal, prosquamosal, and quadratojugal. 4. External process of pterygoid present and covered with small teeth. 5. Parasphenoid rostrum appearing on the lower surface of the skull. 6. Ectopterygoid present. 7. Tabulate present. 8. Cheek teeth simple, conical; one or more than one row in each jaw. 9,10,11,12. Not determinable. 64 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA Table III. — Contrasting the Families of the Cotylosauria. I. Suborder DiaJectosauria. A. DiaJectiJtr. 1. Surface of the sicull rugose or tuberculate. 2. Pineal eye enormous. 3. Occipital condyle flat or concave. 4. A more or less complete armor of dorsal plates and plates overlying the ribs. 5. Anterior ribs, at least, expanded into wide plates. 6. Body low and heavy; neck extremely short; limbs stout and clumsy 7. Tail moderately long, with strong chevrons. B. Bdosaurida. 1. Skull smooth or slightly rugose. 2. Pineal eye small. 3. Occipital condyle rounded. 4. No armor. 5. Ribs not expanded. 6. Body low; limbs short, not heavy. 7. Not determinable. II. Suborder Pareiasauria. A. Pariotichida. 1. Small. Skull rounded anteriorly, flattened, amphibian in appearance. Fine sculpture on the bones of the skull. 2. The basioccipital and basisphenoid united and forming a large plate on the base of the skull. 3. Incisor teeth not enlarged. One or two cheek teeth anterior to the orbit larger than the rest. More than one row in each jaw. B. Caf>torhinida. 1. Small, but larger than the Pariotichtda. Skull acuminate, rugose. 2. Basioccipital and basisphenoid small; not forming a large plate on the base of the skull. 3. Incisor teeth much enlarged, tusk-like. Cheek teeth gradually increasing in size to the middle of the series and then decreasing. More than one row in each jaw. C. Seymourida. 1. Skull size of that of Labidosaurus. A large epiotic notch, quadrate exposed but without pos- terior hook. 2. Basioccipital and basisphenoid small; not forming a large plate. 3. Median incisors not enlarged. Cheek teeth simple cones, none enlarged. More than one row in each jaw. III. Suborder Pantylosauria. A. Pantylidte. 1. Slightly larger than the Capforhinidce. Skull cordiform. Quadrate not exposed. Surface with a particularly close, reticulate sculpture. 2. Median incisors very slightly larger than the others. Cheek teeth in the form of blunt, swollen cones; the second or third larger than the others. Posterior cheek teeth small. 3. More than one row of teeth in each jaw. Table IV. — Contrasting the Characters of the Genera of the Suborder Diadectosauria. Family Diadectidtr. Diadecles (in addition to the characters given under the family and suborder). 1. Middle cheek teeth with three distinct cusps. Number of cheek teeth variable. Tooth line sigmoid. 2. Skull with coarse, rugose sculpture; not tuberculate. 3. The third, fourth, and fifth ribs expanded into triangular plates. The sixth, seventh, and eighth overlaid by slender plates. 4. Transverse processes of the vertebrae extending beyond the zygapophyses. Diasparactus. (Only the vertebrae known.) 4. Transverse processes of the vertebrse not extending beyond the zygapophyses. The centrum relatively small. Bolbodon. (Only the skull known.) 1. Teeth uncertain, perhaps with a single cusp in the molar series. 2. Skull with finer sculpture; not tuberculate. SYSTEMATIC REVISION 65 Table IV — Continued. Family Diadectida — Continued. Chilonyx. (Only the skull known.) 1. Cheek teeth unknown, perhaps cuspate. 2. Skull with coarse sculpture and tuberculate Desmatodon. I. Teeth intermediate between Bolosaurus and Diadectes. Diadectoides. (Only the vertebral column and hind limb known.) and stout limb bones. Family Bolosauridtt . Bolosaurus. 1. Cheek teeth with a single cusp. 2. Skull smooth or slightly rugose. Family Nolhodontidtt (uncertain). Nothodon. I. Cheek teeth with three cusps. Characterized by small size Table V. — Contrasting the Characters of Genera of the Suborder Pareiasauria. Family Pariolichida. Pariotichus. 1. Skull low and rounded anteriorly, resembling that of the Amphibia. 2. Orbits large and located near the middle of the skull. 3. Teeth more sharply conical than in the Captorhinida, but less so than in the Amphibia. 4. One or more cheek teeth anterior to the orbit sharply larger than the rest. Incisors not enlarged. 5. Teeth probably in more than one row in both jaws, but no evidence. 6. Basioccipital and basisphenoid large and forming a broad plate on the base of the skull. 7. Supraoccipital plates standing nearly vertical at the back of the skull. 8. Surface of the skull with fine sculpture. Ectocynodon (very doubtful). Distinguished from other members of the family by rectangular interorbital sculpture. Isodectes. 1. Skull low and rounded anteriorly; amphibian in appearance. 2. Orbits large, located in the anterior half of the skull. 3. Teeth more sharply conical. 4. Indeterminable. 5. Teeth in more than one row in the lower jaws. Maxillary series not visible. 6. Basioccipital and basisphenoid not visible. 7. Supraoccipital plates horizontal in the single specimen. 8. Bones of the skull with a sculpture of fine radiating lines. Family Captorhinida. Captorhtnus. 1. Skull more elevated than in Pariotichus. More acuminate. 2. Orbits large, in the posterior half or the middle of the skull; looking laterally. 3. Teeth obtusely conical or blunt. 4. Maxillary teeth increasing in size to the fourth or fifth and then diminishing. One or all of the incisor teeth enlarged. 5. Teeth in more than one row in both jaws. 6. Basioccipital and basisphenoid not enlarged. 7. Supraoccipital plates vertical at the back of the skull. 8. Skull with a definite reticulate sculpture. 9. Scapula, coracoid, and procoracoid united. 10. Cleithrum present. 11. Ischium and pubis broad and plate-like. Labidosaurus. 1. Larger than Captorhinus. Skull broader behind and more sharply acuminate anteriorly. 2. Orbits large; near the middle of the skull, looking laterally. 3. Teeth obtusely conical or blunt. 4. Maxillary teeth not differing greatly in size. 5. More than one in each jaw {fide Williston). 66 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA Table V — Continued. Family Captorhiniitt — Continued. Lchidosaurut — Continued. 6. Basioccipital and basisphenoid not enlarged. 7. Supraoccipital plates vertical at the back of the skull. 8. Skull with a reticulate sculpture. 9. Scapula, coracoid, and procoracoid united. 10. Cleithrum absent. 11. Ischium and pubis broad and plate-like. Family Seymourida. Seytnouria. 1. The skull a little broader than long; blunt anteriorly. 2. Orbits large, more in the posterior half of the skull than in the middle, looking laterally. 3. Not determinable. 4. Not determinable. 5. Not determinable. • 6. Basioccipital and basisphenoid not large. 7. Supraoccipital plates nearly vertical but occupying a considerable space and are on the upper surface of the skull. 8. Skull with definite, reticulate sculpture. 9. Not determinable. 10. Cleithrum absent. Table VI. — Showing the Characters of the Genus Pantylus. Pantylus. 1. Skull flat on top with the sides steeply inclined; the posterior surface nearly vertical. 2. Orbits of medium size, near the middle of the skull. 3. Teeth, blunt, swollen cones. +. Maxillary teeth nearly uniform in size, except the second or third, which is larger. 5. Teeth in more than one row in the lower jaw and probably in the upper also. 6. Not determinable. 7. Supraoccipital plate vertical. 8. Skull with close reticulate sculpture. 9. 10, II. Not determinable. NOTE. Since the manuscript of this article has been placed in proof two articles have appeared from the pen of Prof. S. W. Williston: 1. Restoration of Seymouria baylorensis Broili, an American Cotylosaur. Journal of Geology, vol. xix, 191 1, pp. 232-237. 2. A new family of reptiles from the Permian of New Mexico. American Journal of Science, vol. XXXI, 191 1, pp. 378-398. In the first of these the author presents a restoration of Seymouria and discusses its habits. The family name Seymouridce is proposed without specific characterization. In the second a new family, Ltmnoscelida, based on the genus and species Limnoscelis paludis, is proposed from material in the collection of the Peabody Museum of Yale University. The new family belongs in the suborder Paretasaurta, as defined in this paper. Its characters as compared with the other families of the suborder are as follows (see table in) : D. Limnosctlidte. 1. Skull large as that of Z)tai?f««. Narrowed in front, broad in the temporal region. Not rugose. 2. Basioccipital and basisphenoid large. The latter well formed and separated from the basioccipital by a well-marked suture. Basipterygoid processes large. 3. Incisor teeth large; the median pair the largest. The cheek teeth conical, largest in tht anterior part of the jaws. Probably only one row in each jaw. MORPHOLOGICAL REVISION 67 MORPHOLOGICAL REVISION. Genus DIADECTES Cope. (Plates 1-9, 14.) Characteristic specimens: No. 4684 Am. Mus. Nat. Hist.; a nearly complete skeleton lacking skull and foot bones. No. 4839 Am. Mus. Nat. Hist.; a nearly perfect skull. No. 1075 University of Chicago; a nearly complete skeleton, lacking only the feet. Nos. 4684 and 4839 have been identified as D. phaseolinus. No. 1075 can not be specifically identified, but it belongs very close to the above specimens, though smaller. In the following description, which may be taken as that of Diadectes phaseolinus, the details are largely taken from the two specimens in the American Museum, as the Chicago specimen has not been cleaned or mounted. The skull of the genus is represented by numerous more or less complete specimens, but none show the internal structure at all well except No. 4839. This is very perfect, lacking only the premaxillary and the articular portion of the quadrate of the left side. The form of the skull is quite similar to that of Pareiasaurus. The posterior end is much wider than the anterior, the sides slope outward and downward, so that the upper surface is nar- rower than the lower; the distance across the top of the skull in the parietal region is not more than half of that across the articular ends of the quadrate bones. The posterior face falls off almost vertically. The top is flat and descends slightly from the posterior to the an- terior end. In most specimens the surface of the skull is covered by a rough sculpture which dimin- ishes anteriorly, but is renewed on the premax- illaries in a series of roughly parallel grooves. The bones are so closely united that the su- tures can not be traced on the upper surface. One specimen in the American Museum shows _ the top of a skull with the cast of the lower F10.19. — Fragmect of the top of tlie «kuU of Difl<&«« surface; on this cast and on the lower surface »p-. »howmg suture.. x4. No. 4845 Am. Mus. of the bones the course of the sutures can be traced. The parietals are large plates surrounding the parietal foramen and reaching to the posterior edge of the skull. The supraoccipital and other (indeterminable) bones form the posterior surface. The large squamosal bones articulate with the parietal, postorbital, and jugal; there is no evidence of the presence of a tabulare. Just anterior to the parietal foramen the suture between the parietal and frontal runs nearly straight across the top of the skull and meets the postfrontal on either side. The frontal is kept from taking part in the orbits by the union of the prefrontal and postfrontal. The parietal foramen is "enormous," as described by Cope. Near the posterior edge of the skull there are deep pits, one on each side, approximately in the line of the suture between the parietal and squamosal. From a study of less perfect specimens these have been reported as probable rudimentary openings, but in these specimens they are certainly closed at the bottom. This character seems to have been extremely variable, recalling the condition in the Pelycosauria where the supratemporal opening may be persistent or may be closed. Posterior aspect: The occipital condyle is wider than long and is excavated on the upper border by the foramen magnum, so that it presents a broad heart-shaped 68 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA outline. The articular face for the atlas is concave and there is a deep pit for the continuation of the notochord; it slants downward and forward, so that if it were applied to the atlas without a large preatlantal intercentrum the skull would have been carried almost at right angles to the vertebral column. The foramina for the exit of the posterior cranial nerves are not apparent, but deep pits on the sides of the basioccipital may have led into the openings of the foramina. The limits of the various bones forming the posterior plate of the skull can not be Fig. lo. — Skull of DiadtcUt fhastelinus. X }• No. 4839 Am. Mus. A, Uteral Tiew, tbowing probable arrangement of tuturet; B, lateral view; C, posterior view; D, top Tiew; E, lower Tiew. made out, as the sutures can not be traced, but it is apparent that the paroccip- ital bone was short, and joined, almost at once, the descending processes of the squamosal and the quadrate. I have described two perforations in the posterior portion of the skull in the position of posttemporal foramina and likened the con- dition to that of the turtles (Case 15); in this specimen I find only two deep pits in this position. Lateral surface of the skull: The quadrate rises almost vertically, the anterior border is attached to and somewhat overlapped by the bones of the postorbital MORPHOLOGICAL REVISION 69 region. Near the upper end the quadrate turns to the rear and joins a process of the paroccipital; the turn in the quadrate is marked by a sharp angle quite similar to that seen in the same position in the turtles. No traces of a columella was found and if present it must have been very short. The opening of the auditory canal can not be made out, but it must have been almost oppositejthe angle described. The outer face of the quadrate is concave, form- ing a funnel-like cavity with the apex at the notch de- scribed above. The whole surface of this concave face is smooth, and anteriorly it is overlapped somewhat by the posterior edge of the squamosal The posterior edge is covered by a bone whose upper limits can not be Fio.h. — Lateral view of skuU determined, but which is separated from the quadrate °' '^'"'°'" '""^'• below by a quadrate foramen of good size. The articular face of the quadrate for the lower jaw is wider than long, convex, and is divided into nearly equal parts by a shallow groove running anteroposteriorly. The sutures between the bones are no more distinct than on the superior sur- face, but the slight crushing of the specimen has caused some of the bones to break apart slightly, and this with some slight traces of sutures warrants the following con- clusions as to bones of the side of the skull.* The squamosal is continued backward at the upper end in a process which overhangs the quadrate and may contain the tabulate, but there is no suggestion of a division. This portion of the bone bears a striking resemblance to the same region in the turtles. The anterior edge of the squamosal is convex forward and joins the postorbital and prosquamosal. The prosquamosal covers the quadrate below and articulates posteriorly with the bone which covers the posterior surface of the quadrate and is separated from it by a foramen; this I consider the quadratojugal. Anteriorly, the prosquamosal articulates with the jugal. It will be seen that this bone occupies the position occupied by the quadratojugal in many reptiles. The reason for considering this bone to be a prosquamosal is given in the discussion of the genus Captorhinus, where the position and form of the bones are shown much more clearly (see p. 94). The quadratojugal lies on the back of the skull, covering the posterior surface of the quadrate and separated from it by a large quadrate foramen; its limits can not be made out, as no sutures are traceable on the outer surface of the skull. This interpretation of the temporal region of the skull is radically different from that assumed by Cope. He believed that the Diadedidee had the full complement of bones, such as he figured in Captorhinus (Pariotichus), and upon this basis considered the Cotylosauria as possessing the most primitive type of skull, the one from which all other reptilian types were derived. The impossibility of the Cotylosauria occupying such an ancestral position is apparent, and the equal impos- sibility of any other known form from the Texas Permian occupying such an ancestral position is demonstrated in the discussion of the different groups. The jugal forms the lower edge of the orbit; the suture between it and the max- illary is not certain. The maxillary probably forms a part of the lower edge of the orbit. It does not reach far up on the side of the facial region. The number of teeth in the upper jaw, maxillary and premaxillary, is given in the following list as accurately as they ♦In thi« detennination I wa» aided bjr Dr. Broom of Victoria College, Cape Colony, and at we reached a perfect agreement on the determination! it ii advanced with tome confidence. He give*, howcTer, different names to some bones, as quadratojugal for the bone called here prosquamosal. In his recent paper (lOa) he gives a figure of sutures differing slightly from the figure here given, fig. io,A. 70 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA can be determined. These figures are in part estimates, as the upper jaws are imperfect in some specimens. No. 4350 Am. Mas., D. molaris 14 No. 4349 Am. Mus., D. phaseolinus 14 ^ No. ^S^gAm.Mus., D. phaseolinus 14 No. 1078 Univ. of Chicago Z)ta/mui, xj No. 4839 Am.Mus. Aftraotverte wction; B, longitudinal section of same, al, alispbenoid; als.r, alisphenoid of right tide; iip, basiiphcnoid; is, banoccipital; M/t, ethmoid; ^, pterygoid; ^.r, prevomer of right tide; mx.r, maxillary of right side; 0, orbit; V| opening for escape of cranial nerves. Between the palatines (maxillary plates of Cope) there is left quite a space, in which lie the prevomers. These are vertical plates of considerable height, but very narrow on the palatal surface. Towards the posterior ends the upper edges of the plates flare outward to join the palatines or pterygoids, but at the anterior end the plates are vertical and parallel; the upper edge touches the lower edge of a median vertical plate described below. There are traces of a few large conical teeth on the prevomers, but they are sparse and irregularly arranged. Longitudinal section of the skull: The brain case shows the sharp downward bend posterior to the epiphysis described by Cope in his account of the cast of the brain cavity. Anterior to the optic region there is a very large foramen which gave exit to the seventh nerve; it is likely that other nerves escaped through the same opening. Anterior to this foramen the walls of the brain case are formed by solid elements, the alisphenoids, which are attached to the under side of the roof above and to each other and the basisphenoid below. They may be traced as far forward 72 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA as the anterior edges of the orbits. Just anterior to the epiphysis of the brain the bones of the two sides meet below, inclosing a long narrow cavity which remains open in front. This sheltered the great elongation of the nasal lobes and the ante- rior portion of the brain shown in Cope's cast. Anterior to the basisphenoid and joining the short anterior rostrum is a single vertical plate. This ends somewhat abruptly behind, where it joins the basisphenoid but extends upwards until it touches the alisphenoids above. It remains in con- tact with these bones to their anterior ends and from there forward is joined by cartilage to a prominence on the lower surface of the nasals. The lower edge of its anterior half is in contact with the upper edges of the prevomers. This bone is similar in all respects to that figured by Broom in Lystrosaurus and by the author in Dimetrodon as the ethmoid or true vomer. It is in direct continuation with the parasphenoid rostrum, if it is not an actual part of it. The brain: The following account of the brain is transcribed directly from Cope's account (30). "The brain-case in the Diadectidee differs from that of the Clepsydropidce much as that of the Varanidee differs from those of other Lacertilia. That is, it is continued between the orbits, so as to inclose the olfactory lobes of the brain within osseous walls. These walls are thin; especially at the interorbital region, and in the specimen the anterior extremity is so far imperfect as to leave the form of the anterior fundus in doubt. * * * "The formation of the cranial walls requires preliminary notice. In the first place the vestibule of the ear can only have been separated from the brain by a membranous septum, as is the case in the Protonopsis horrida* (Menopoma). In clearing out the matrix no trace of osseous lamina could be detected on either side and the edges of the huge foramen thus produced are entire, and present no broken edges. Anterior to the vestibule, the prootic bone has a small extension, terminating in a vertical border. In front of this is a huge vertical foramen through which issues the trigeminus nerve which is even larger than that found in the Testudinata and Crocodilidce. The anterior border of this foramen is formed by the probable alisphenoid, whose posterior edge is nearly parallel with the anterior border of the prootic, sloping forwards as it descends. The basicranial axis is thin at their union on the middle line below, and, thickening forwards, is excavated by a rather small conical fossa. Anterior to the fossa is a smaller impressed fossa, and on either side of it, each lateral wall is excavated into a shallow fossa which descends towards it. The frontoparietal fontanelle is of extraordinary size. " I. THE BRAIN. "When the superior border of the medulla oblongata at the foramen magnum is placed horizontally, the axis of the brain ascends at an angle of 45° towards the frontoparietal fontanelle. The superior surface, anterior to the foramen magnum, is subquadrate in outline, the angles being truncated, and directed anteriorly, posteriorly, and laterally. A posterior constriction connects it with the medulla; and an anterior one defines the middle brain and hemispheres. Each lateral truncated angle represents the foramen of the trigeminus nerve. The space thus bounded is divided into two nearly equal areas by a transverse groove, which extends from the posterior edge of one of these foramina to the other. The posterior of these I suppose to represent the cerebellum, and the anterior the optic thalami. The cerebellar surface indicates that, as in many lizards, the cerebellum is simple, and very slightly convex. * Sec Journal Academy Philadelphia, 1866, p. 105, where the charaaert of the skull in the Vrtdela are pointed out. MORPHOLOGICAL REVISION 73 "Anterior to the foramen trigemini, the brain contracts so as to have a trans- verse diameter scarcely more than one-third its vertical diameter. The cast at a point twice as far in advance of the cerebellar line as the fore-and-aft width of the cerebellum, rises to fill the frontoparietal foramen, forming a mass which represents the huge pineal sac or epiphysis. The proportions of this body are even greater than they are in any of the existing Lacertilia, and it has a greater transverse diameter than the middle brain inferior to it. Its posterior border is at right angles to the line continued forwards from the superior border of the medulla oblongata at the foramen magnum. At its posterior base a flat horizontal processs, as wide as the brain at this point, extends posteriorly in a corresponding fossa of the superior cranial wall. Its posterior margin occupies a transverse groove of the superior wall between the superior and inferior plates. Each lateroposterior angle is pro- duced, and may represent the foramen of exit of a narrow canal which appears to perforate the lateral wall and issue beneath the roof of the temporal fossa. A large projection of each side of the base of the epiphysial mass occupies a large foramen of the lateral wall, which has the superior wall for its superior border. This may only represent a vacuity of the wall, but the fossa at the posterior base of the epiphysis has greater significance. What this is I am at present unable to ascertain. "Below the epiphysis the transverse diameter of the brain is about one-fourth the vertical, not including a short inferior prominence. The latter is small and conical, and is situated below the center of the epiphysis when the cerebellar surface is placed horizontally, or in front of it, when the medulla at the foramen is placed horizontally. Its significance is unknown to me, as it is anterior to the position of the hypophysis. A thickening of the cast on either side of its base converges to the median line posterior to it. I can find no optic foramina, and believe, therefore, that the optic nerves issued from the same large sinus as the trigeminus. The cast diminishes in vertical diameter anterior to the inferior conical process, and increases in transverse diameter of its superior surface. The inferior border continues to be keel-like, so that a vertical section is triangular with the base superior. It is impossible to distinguish the outlines of the cerebral hemispheres or the olfac- tory lobes, both of which are probably included in this part of the cast, although the latter probably extended much anterior to the extremity of the brain case as preserved. The form may or may not give an idea of the forms of the hemi- spheres. In any case they were narrower than in any known reptile. "The prominent features of this brain are then the following: The widest part is at the origin of the trigeminus nerve. Both the cerebellum and optic thala- mus are flat and simple. The hemispheres are narrower than the segments posterior to them and of greater vertical diameter. The epiphysis is enormous, and sends a process posteriorly between the tables of the parietal bone. The olfactory lobes were apparently large, and had a greater transverse diameter than the hemi- spheres. The reduced diameter of the hemispheres is a character of fishes and Batrachia rather than of reptiles, but the thalami are also smaller than is the case in Batrachia. The small, flat cerebellum is rather batrachian than reptilian. " 2. THE AUDITORY APPARATUS. "As already remarked, the internal wall of the vestibule is not bony, so that the cast of the brain cavity includes that of the vestibule also. On the external wall of the latter are the orifices of the semi-circular canals. These are, one double fossa at the superior-anterior part of the wall; a second double one at the posterior- superior part of the wall, and a single orifice at the inferior-posterior part of the wall. The external part of the vestibule is produced upwards and outwards to the 74 A REVISION or THE COTYLOSAURIA OF NORTH AMERICA fenestra ovalis. The "double fossae" above mentioned are the osseous represen- tatives of the membranous ampullae at the junction of two pairs of semicircular canals. "On sawing open the periotic bones, which here form a continuous mass, the following is seen to be the direction of the semicircular canals. The superior canal is horizontal. The second canal, from the posterior ampulla, descends forwards and, after a course a little longer than that of the horizontal canal, turns posteriorly. The inferior canal from the anterior ampulla also descends and, after a shorter course than the canal last mentioned, also turns backwards and joins it, the two forming a single canal, which enters the vestibule by the single posterior foramen already described. The lumen of the longer perpendicular canal is much larger than that of the others. As its ampullar orifice is also the largest of all, 1 suppose this increased diameter to be partly normal; but it may be partly abnormal, as its walls are irregular and rough. "The fenestra ovalis is not preserved in this specimen, but can be seen in. the cratiia of the species Diadectes phaseolinus and Empedias molaris above mentioned.* The vestibule or a diverticulum from it is produced upwards and backwards, and terminates in a round os. This is clearly not a tympanic chamber, nor is it a rudimental cochlea. It does not appear to be homologous with the recessus laby- rinthi, since that cavity is not perforated by the fenestra ovalis. It appears to be a prolongation outwards of the vestibule and sacculus, which may be observed in a less degree in the genus Edaphosaurus (Cope), also from the Texas Permian forma- tion. Here the adjacent bones are produced slightly outwards, and the fenestra ovalis is closed by a large stapes similar in external form to the one I have described in the Clepsydrops leptocephalus.^ Its more intimate structure I have not yet examined, j "The result of this examination into the structure of the auditory organs in the Diadectidcs may be stated as follows: The semicircular canals have the structure common to all Gnathostomatous Chordata. The internal wall of the vestibule remains unossified, as in many fishes and a few batrachians. There is no rudiment of the cochlea, but the vestibule is produced outwards and upwards to the fenestra ovalis in a way unknown in any other family of vertebrates." The lower jaws (plate 4, fig. 2) of specimen No. 4684 are nearly complete, lacking only the articular region of the left side. There are three pairs of large incisors (the median pair the larger) and eleven cheek teeth. In specimen No. 1076, University of Chicago, there are three incisors and twelve cheek teeth; the discrepancy is probably due to the loss or obscuration of a tooth in No. 4684. The incisors have a greater anteroposterior diameter than transverse and the inner side shows a worn surface. The front two teeth after the incisors are small with a single cusp, but rapidly increase in size posteriorly through the third, fourth, fifth, and sixth; the seventh is the largest, the tenth and eleventh are abruptly smaller. The shape of the tooth is well shown in the figure of the type (plate i, fig. 6, 6a). Opposite the largest teeth the jaw is widened, not only by the increase of the alveolar surface but by the retreat of the tooth line from the outer edge of the jaw, which remains nearly straight. The separate bones of the jaw can not be made out; they *Sce ikull of E. nia/arii,Proc. Amer.PhUoiopb. Society. iSSt, plate v, 6ga. a and t, where the feneitra ia represented. fSee Proc. Amer. Philotoph. Society, 1884, p. 41 . tProfeaaor Ouxn hat figured (Todd's Encyclopedia, art. Monottemata) a structure in Echidna, which looks remarkably like that here described. This it a tubular elongation of the meatus auditorius cxtemut with more or Irss cartilaginous walls. This structure might be regarded as homologoutwith that displayed by the Emptdlai, couM we imagine that with their diminution in size in the Monotrcme, the otticula auditut had retreated within this tube preceding the membranum lympani, from a position at its distal to one at iti proximal extremity. But tiich a tuppotition has at yet no foundation, and the very limilar parts in the two types may hare no homology. MORPHOLOGICAL REVISION 75 Fig. ij . — Inner view of right lower jaw of DiaJecUt ip, x J. No. 1076 Univ. of Chicago. are as closely united as are the bones of the skull. Just within the low coronoid process there is a large opening on the inner surface of the jaw admitting to a large cavity and a second one on the same side near the anterior end. The outer surface of the jaw is covered with a rough irregular sculpture. The lower jaw of specimen No. 1076 University of Chicago (plate 6, fig. 3) differs in some details from that of No. 4684 Amer. Museum. The jaw is singularly testudinate in general appearance. The anterior portion is relatively very high and the coronoid process is inconspic- uous. The anterior portion of the jaw descends slightly to the symphysis, which is narrow, sutural, and formed almost entirely by the dentary. Just anterior to the coronoid there is the enormous posterior opening of the Meckelian cavity, and (a short dis- tance anterior to this) a second open- ing. The narrow bridge separating the two is probably formed by the dentary. The alveolar border is broad and the teeth are placed near the inner edge, being separated from the raised outer edge of the dentary by a shallow groove. It is impossible to determine the outline of the separate elements. There are eleven cheek teeth and at the posterior end the alveolus for a small one. Anterior to these is a single incisor and alveoli for four more, making six- teen in all. This is more than in other specimens. The vertebral column (plate 4, fig. 3; plates 6, 14). The complete presacral f>ortion of the column in the University of Chicago specimen, No. 1075, has twenty- one vertebrae. The American Museum specimen, No. 4684, lacks the atlas and axis and there is one break in the column where the parts do not fit. As mounted, this specimen has twenty vertebrae. There are two sacrals and a large number of cau- dals, thirty-three in the specimen as mounted, but ten of these are restored in plaster to supply evident gaps. The exact number is uncertain. The atlas, determined in part from specimen No. 1075 University of Chicago, has a simple disk-like centrum with the neural arch free and separated into two halves. As described above, the articular face of the occipital condyle is strongly inclined to the axis of the skull, so that there must have been a large preatlantal intercentrum to enable the skull to be held in line with the body. The neural arches strongly resemble those of DimetroJon; they are semicircular in shape; the inner face is divided by a ridge into an upper half which protected the spinal cord and a lower half which articulated with the centrum. The anterior end of the upper half extended forward so as to touch the surface of the skull just above the foramen mag- num. On the outer surface of each half is still attached the broken anterior zyga- pophysis of the axis. Articular faces for ribs can not be detected. The axis has the neural spine only slightly higher than those of the succeed- ing vertebrae, but of very different form. It is thin laterally and of considerable anteroposterior extent. The posterior edge is thicker and nearly vertical, but the anterior edge slopes downward and forward and terminates in a very thin margin, possibly extending between the halves of the neural arch of the atlas. The anterior zygapophyses are small, the posterior full size, and the articular faces of both are hori- zontal. There are well-developed transverse processes. The intercentrum between the axis and the atlas was small; this seems to have been the condition throughout the column with the exception of the preatlantal intercentrum. 6 76 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA The third vertebra has the posterior zygapophyses more obliquely placed. The spine is stout and short, somewhat diamond-shaped in section, with the edges anteroposterior. The sides are very rugose and there is on each side a triangular flap extending to the rear to increase the surface for the attachment of the nuchal ligament. The transverse process is short and there is a very short face for the tuberculum of the rib on its distal end. There is no face for the capitulum, though there was a well-developed head on the rib; it must have been attached to the inter- centrum. The lower edge of the transverse process is not free from the centrum, but attached to it by a broad thin plate of bone, as is so characteristic for the whole group. The centrum is round in section and there are no median or lateral keels on the surface. It is shorter be- low than above, leaving a space for the intercentrum. On the fourth cervical the anterior zygapophyses are ob- lique, but the posterior ones are horizontal. The spine is shorter and stouter than that of the third. The transverse process is wider, but still supports only a single facet for the rib. On the anterior edge of the centrum, near the bottom, is a facet for the capitulum of the rib. In the fifth the facet for the capitulum is united with the one on the transverse process by a very narrow ridge; this corresponds with the fact that the capitulum and tuberculum are practically united in the rib. All the vertebrae of the presacral series have the strong hyposphene-hypantrum articulation in addition to zygapophyses. This structure was first described by Cope in the dinosaurian genus Amphicalias as follows: "The anterior zygapophyses are separated by a deep fissure, while the posterior zygapophyses are united on the middle line. From the latter, from the point of junction, there descends a vertical plate which rapidly expands laterally, forming a wedge whose base looks downward. The supero-lateral faces are flat, and articulate with corresponding facets on the inferior side of the anterior zygapophyses, which look downward and inward, on each side of the fissure above described. When in relation, the anterior zygapophyses occupy a position between the posterior zyga- pophyses above, and the hyposphene, as I have termed the inferior reversed wedge, below. This arrangement accomplishes the purpose eflPected by the zygosphenal articulation — that is, the strengthening of the articulation between the neural arches, but in a different way. The additional articulation is placed at the opposite extremity of the vertebra, and it is the anterior zygapophysis instead of the posterior which is embraced." In the sixth the two facets on the transverse process are completely united and the vertebra has taken on the character of a true dorsal. The wide, wing-like transverse processes bear a single face which slopes downward and forward as well as inward. The upper part of this facet is much broader in the anterior vertebrae, but gradually decreases until in the mid-dorsals and posterior dorsals it is only at the extreme upper end that this can be noticed. Throughout the series the rib heads are not so long as the faces on the transverse processes; there was evidently Fig. 14. — Dorul vertebra of Diadecut sp. X ). No. 4840 Am. Mus. a, anterior view; h, lateral view. h MORPHOLOGICAL REVISION 77 a considerable quantity of cartilage present in the joint. The centrum is more oval in section than in those anterior to the sixth. The spines of the vertebrae from the sixth to the tw^elfth are exceptionally low and stout, with the distal ends very rugose, either with a median notch or the top expanding like a mushroom, evi- dently to afford attachment to strong ligaments or perhaps to overlying dermal plates. With the thirteenth the vertebrae are broader and have less anteroposterior extension of the neural arches and zygapophyses. At the same time the neural arch and spines become higher, so that the whole posterior dorsal series looks thinner and more elevated than the anterior. The articular faces of the transverse processes here begin to shorten and on the fifteenth and sixteenth they reach forward to top of centrum; the lower end no longer passes gently into side of centrum, but stands out abruptly from it. This continues to the twentieth, and on the twenty-first, the first presacral, the transverse process is suddenly shortened and fused with a very short rib. There are two sacrals. The spines are abruptly bent backward, leaving a considerable space between the first sacral and the straight spine of the first presacral. The anterior zygapophyses of the first sacral are full-sized, but the articulation between the two sacrals is so close that the zygapophyses have practically disap- peared. The rib is very stout and strong and the distal end is widely expanded and applied to the inner surface of the ilium. The rib of the second is smaller, the distal end less expanded, and it appears to be, in part at least, applied to the expanded surface of the first rib. The intercentrum between the two is fused with the centra. The first caudal has the spine sharply curved backward, resembling in this respect the sacrals. The ribs are stout and fused with the transverse processes. The anterior zygapophyses are small, but larger than those between the sacrals. The hyposphene and hypantrum are small but distinct. In the second caudal the spine is still recurved and the zygapophyses are large and well formed, but there is no trace of the hyposphene and hypantrum. The ribs are elongate and sharply bent to the rear. The third to fifth caudals diminish regularly in size; the spines are straight and the zygapophyses are proportionately larger than in the first two. The transverse processes are large, increasing the width of the vertebrae. The ribs of the fourth and fifth are reduced in length. The first chevron appears between the fourth and fifth, or the fifth and sixth, and continues to the extremity of the tail. The sixth to ninth. The transverse processes are much shorter and with the rudimentary ribs stand straight out from the side of the centrum. The centrum is shorter, so that these vertebrae look wider than those before or behind. On the tenth is the last trace of a rib; behind this there are only rudiments which rapidly disappear. The vertebrae from the tenth to the twenty-fifth are similar to the tenth; retaining the high spines as they diminish in size, they are more slender in appearance. Twenty-sixth to thirty-third. There are thirty-three vertebrae in the tail as mounted; ten of these are plaster models, necessary to complete the sequence, and there were probably a few, four or five, missing at the tip of the tail. Shortly after the twenty-fifth the vertebrae lose their spines and assume an elongate form, though they never approach the proportion seen in forms with elongate, taper tails. The chevrons are exceptionally large and lie fairly close to the centra. The upper end is perforated by an elongate foramen which is not complete above, in the anterior part of the tail, but in the middle and posterior part of the tail is closed. The ribs. Imperfect remains suggest that the ribs of the atlas and axis were fairly long and slender. That of the third was an elongate plate of triangular form with the anterior edge straight and an angle to the rear overlapping the rib of the 78 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA fourth vertebra. The capitulum and tuberculum are distinct, the first reaching to the intercentrum and the latter touching the end of the transverse process. The fourth resembles the third, but is much larger. The capitulum and tuberculum are separated by a slight notch only. The capitulum is attached to the facet on the anterior edge of the fourth vertebra. The whole rib is larger and the point on the posterior edge larger than the third. The fifth rib is much larger than the third and fourth, but the posterior prolonga- tion is less marked than on the fourth. The capitulum and tuberculum are hardly distinct, thus corresponding to the position of the facets on the vertebra; the one on the anterior edge of the centrum extends backv?ards toward the one on the short trans- verse process until the two nearly meet. The expanded ribs overlap each other from before backwards, forming a strong protection for the thoracic region (plate 8, fig. i). Fig. 15. — a. Third, fourth, and fifth ribs of Diadecies phaitolinus. x J. No. 4684 Am. Mui. &, heads of three dorsal ribs of same specimen. Posterior to the fifth, the ribs become normal in form. The sixth is nearly or quite the longest and beyond this the ribs gradually shorten. The tuberculum and capitulum are united in a single facet, but in no place is the face on the end of the rib as long as the face on the transverse process; the lower end of the rib face was attached to the transverse process by cartilage. Overlying the sixth, seventh, and eighth ribs were thin, elongate dermal plates which overlapped each other from before backwards and carried the protection of the thoracic region backward as far as the distal end of the scapula (plate 5, fig. 5). In the previous description of Diadectes by the author (13) it was stated that there were five plates overlying the anterior ribs. This was an error due to the condition of the specimen in which the scapula overlay the ribs, and the edges of the expanded fourth and fifth ribs were mistaken for the edges of plates. Later, the scapula was removed from one side and the true condition made out. The condition of the ribs and the overlying plates is now known from two specimens. In connection with the plates overlying the ribs .should be mentioned the con- dition of the neural spines. In all specimens of Diadectes the upper ends of the spines are expanded and rugose, suggesting very strongly the presence of a row of dermal plates down in the middle of the back. The spines appear much the same as those of Pareiasaurus, in which such a row of plates is known to occur. MORPHOLOGICAL REVISION 79 The shoulder girdle is best known from No. 1075 University of Chicago, but the imperfect girdle of No. 4684 American Museum verifies the determinations. As a whole, the thorax was very narrow; the clavicles and interclavicle are tightly bound together and in the University of Chicago specimen retain their position undistorted, showing the space between the clavicles to have been relatively small. The shortness of the neck brought the anterior end of the clavicles very close to the angle of the lower jaw. The interclavtcle (plate 5, fig. 3) is an elongate bone, rather oval in section, terminating posteriorly in a slightly rugose point. The anterior end was thickened and somewhat expanded; its upper sur- face was smooth, but the lower face was marked by a deep notch the sides of which are formed by the thickening necessary to accommodate the articular surfaces for the clavicles. The clavicles are thickened at the proximal end, where they unite with the interclavicle and with each other anterior to the interclavicle. The union of the clavicles and interclavicle is very close and is accomplished by strong interlocking processes. Beyond the articulation, the clavicles extend out from the interclavicle horizontally for a short distance and then bend sharply to the rear. There are no articular faces at the point of contact with the scapula and cleithrum, but where the blade of the clavicle turns, the upper edge is bent inward and downward, overlapping the edge of the scapula. The cleithrum lay on the outer side of the posterior end of the clavicle. There are specimens of clavicles and interclavicles which are so different from those of the more complete skeletons that they might serve as the basis of new species or genera were it advisable to establish new forms on such fragmentary material. One of these (No. 4390 Am. Mus. Nat. Hist. Cope Coll.) shows the clavicles with about the same relative curvature and included space as those described above, but there is not the deep notch on the lower face of the interclavicle. Another specimen (No. 4771 Am. Mus. Nat. Hist. Cope Coll.) belongs to a much larger animal. The clavicles are more gently curved and there is a much wider space between them. There is no evidence of distortion due to pressure, but it may be that this is responsible for the lesser curvature. As the clavicle of the left side only is present, the matter must remain in doubt. The scapula (plate 5, fig. i, and text fig. 27) is as shown in figures. The cora- coid and procoracoid are not separated from the scapula by suture. The posterior end terminates in a point formed by a slight excavation of the upper border. A separate specimen consisting of the scapula and humerus of the left side only (No. 4709 Am. Mus. Nat. Hist.) and belonging to a large species of the genus permits of the best description. The anterior edge is nearly straight and shows the attachment of a cartilaginous epicoracoid of considerable size. On the superior Fig. 26. — Anterior view of the claviclet and interclaricle of Diadectti %f. x}. iWon it. There was no neck, and the thoracic region was much more narrow than might have been expected. The limbs were very powerful, but exceedingly short, and as the motion of the humerus was closely limited to a forward and backward movement in the horizontal plane, the movement of the limbs must have been like that of the turtles. Viewed from the front, the heavy head and short limbs, with the humeri standing almost straight out from the scapulae, give the animal a very testudinate appearance. The expanded thoracic ribs and the plates over the sixth, seventh, and eighth are in keeping with what seems to be a general tendency in adaptation during the period. Many of the herbivorous reptiles and amphibians show an expansion of the ribs with or without an accompaniment of overlying plates; this was perhaps an attempt to resist the attacks of such fiercely carnivorous forms as Dimetrodon, in a time before agility of body or high intelli- gence had become possible adaptations. No attempt has been made to represent a dorsal armor, but the character of the terminations of the neural spines, the numer- ous parallel adaptations with Pareiasaurus in which such plates occur, and the numerous instances of a dorsal armor in coexisting forms render it very probable that there was such a protection, at least in a rudimentary state. The wide, short feet with the strong blunt nails suggest the land turtles more than any other type. The tail resembled that of the modern Crocodilia in form and proportions. In looking about for a modern reptile with which to compare it, Heloderma seemed the nearest in many respects. If the limbs of this lizard were shortened, the claws turned to nails, and the bulky tail fashioned into that of a croc- odile the resemblance would be very exact. The habits of the creature are at least indicated. Herbivorous, of low brain power, sluggish in action, it can only have occupied a purely defensive attitude towards such animals as the carnivorous Pelycosaurs. The strong girdles, power- ful limbs with well-formed articulations and especially strong rugosities for muscular attachment, the closely knit and well-formed carpus and tarsus, all indicate a terrestrial habit. The broad, short feet, with large spatulate terminal phalanges which were covered by powerful nail-like claws, strongly resemble those of certain fossorial forms, such as the gopher turtle of Florida, Gopherus polyphemus. It seems probable that the foot rested fairly flat on the ground v«th a pad raising the * Annalt South Airicut Muteum, vol. iv, pt. u, 190}. MORPHOLOGICAL REVISION 85 carpus and tarsus slightly. A small fragment of shale from the same region in which this specimen was found carries the impression of two feet of a smaller animal, but indicates that the foot was elevated, as only the impression of the claws and of a flat pad are shown. I believe these animals to have been harmless, sluggish, terrestrial herbivores, possibly fossorial in habit, at least to the extent of excavating burrows for their protection. The attitude was habitually prone and they could not elevate the body on the limbs even so much as the Crocodilia, nor could they develop any speed even for short intervals. PHYLOGENETIC POSITION. The Diadectosauria have long been regarded as the nearest known form to the primitive ancestor of all the reptiles. This idea must be completely abandoned for the suborder. Aside from the extreme degree of specialization in all parts of the body, which shows how far it is from the primitive line, the structure of the skull makes it impossible that such types as double and single arched reptiles could have been derived therefrom, at least in the simple manner long believed. In fact, the greater our knowledge of these primitive forms becomes, the less certain are we of the primal origin of two great stems from a form with a complete roof. The Rhyn- cocephalian double-arch structure of the skull can not be derived from that of Diadectes or any other known Permian reptile which is not^far too highly specialized in other characters to make its consideration worth while. In a previous discussion of these forms (32) the author has suggested the possible ancestral relationship of the suborder Diadectosauria to the turtles. It is not assumed that this relationship is direct, but the specific resemblances, as well as the general effect of the mounted skeleton, indicate very strongly that they were not far from the ancest ral form of the turtles. The specific points of resemblance as first stated are as follows: 1. The form and relations of the quadrate. II. The degenerate palate and the disappearing transverse bone. III. The absence of teeth on the palatines and pterygoids. IV. The absence of a parasphenoid rostrum attached to the basisphenoid bone. V. The absence of prevomers and the presence of an anteriorly placed single vomer (parasphenoid.) VI. The method of entrance of the internal carotids into the brain cavity. VII. The presence of paired descending plates from the roof of the skull anterior to the brain case. Of these numbers, IV, V, and VI must be modified. IV. Several specimens show no traces of an attached parasphenoid rostrum; this one. No. 4684 Am. Mus., shows a short and degenerate process. Versluys has recently brought evidence to show that Dermochelys has a distinct parasphenoid (36). V. This is wrong. There is a separate parasphenoid (vomer) and distinct paired prevomers in the median line. VI. In some specimens there are no foramina perforating the lower surface of the basisphenoid; in this there is a single large foramen. The original conclusion seems still to be justified. Moreover, it will be at once seen how close is the resemblance of the squamosal and quadrate bones to the same elements in the turtles. If the quadratojugal and with it the quadrate fora- men were to disappear, the condition of the turtles would be exactly realized; for in 86 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA the turtles the squamosal extends backwards overlying and surrounding the upper end of the quadrate. This is exactly the position of the squamosal or squamosal-j- tabulare in the Diadectida: the direct fusion of squamosal and tabulare would produce the condition of the testudinate squamosal. Diadectes molaris Cope . . . . (p. 15) Diadertes latibuccatus Cope ... (p. 19) Diadectes biculminatus Cope . . (p. 17) Diadectes maximus Case . . . . (p. 20) Diadectes fissus Cope (p. 17) Diasparadus zenos Case .... (p. 21) These species are all so incompletely known that an extended morphological discussion is impossible. The known facts are set forth in the systematic discussion. Chilonyx rapidens Cope. (Plate 10, fig. 2.) Characteristic specimen: The type, No. 4357 Am. Mus. Nat. Hist. Cope Coll. This genus probably held the same relation to Diadectes that Geikia did to Pareia- saurus, Miolania to other pleurodrian turtles, or that Phrynosoma does to related lizards. The development of bosses and bony horns is probably an expression of Fio. 32. A. Upper surface of tkult of Chilonyx rapidem. Sutures according to the author, x \. No. 4357 Am. Mus. n, nasal; mx, maxillar;; /, frontal; pj, prefrontal; ptf, postfrontal; po, postorbital; p, parietal; sq, squamosal; qj, quadratojugal; ep, tabulare; to, supraoccipital plates. B. Restoration of skull of Chilonyx, upper view. After Cope, pmx, premaxillary; n, nasal; mx, maxillary; p€J, prefrontal; po/, postfrontal; /, frontal; y,jugal; s, zygomatic; p, parietal; im, squamosal; jf, prosquamosal; in/, tabulare. C. Restoration of skuU of CAiVenyjr, lateral Tiew. After Cope. pmAr, premaxillary; mx, maxillary; n, nasal; /, lachrymal; pej, prefrontal; /, frontal; pob, postorbital; pa/, postfrontal: sm, squamosal; i/, prosquamosal; int, tabulare; z, zygo- matic; ;, quadrate. the same force which led to the development of spines in Naosaurus and Dtmetro- don and to similar extravagances in the Amphibia of the same beds. We have here a glimpse of overspecialization among the Diadectids, perhaps presaging their extinction. In the original description of the genus (25) Cope writes as follows: "The condition of the specimen is such that the composition of the skull may be readily made out. The postfrontal bones are large, and form the superior border of the orbit. At the front of the orbit they reach the prefrontal, thus excluding the frontal. The parietal bones are wider than the frontals, and are bounded laterally by the postfrontals and the squamosals and by an element between the squamosal and exoccipital, which occupies the position of the intercalare of the Stegocephali. Below this bone, on the inner side of the suspensorium, is the probable prootic. The squamosal, or an element which I can not distinguish from that bone, extends to the condyle of the quadrate, concealing that bone from external view. The MORPHOLOGICAL REVISION 87 quadrate is short and thins out rapidly upwards, being closely united with the squamosal. Its condyle is set at an angle of 45° with the axis of the skull, and consists of one flat and one convex surface; continuous but forming a deep angle together. Exterior to the exoccipital, and interno-inferior to the intercalare, is a small distinct element, apparently in the position of an opisthotic or external occipital. "The excavation for the auditory apparatus appears to be in the exoccipital. It is almost entirely filled by what I suppose to be a large stapes. This bone is in shape like a compressed flask, with the head directed inwards and forwards, and its inferior edge produced into a prominent keel, which is produced into a point below, and free from the neck of the flask. The head is truncate and is separated from the internal cranial wall by a narrow interspace. Its external extremity is not absolutely perfect in the specimen, but does not appear to have extended in an ossified condition beyond the exoccipital bone. In a specimen of Empedias molaris* there is a meatus auditorius, in which the stapes was not found on cleaning out. This element is coosified with the surrounding bones laterally and posteriorly. Consequently when broken open, the vestibule is represented by two deep grooves, directed inwards and anteriorly." In 1892 Cope (35) says: "Chilonyx agrees with the Stegocephalia and with other Diadectidce in posses- sing a distinct intercalare (tabulare). The component elements of the cranial roof are equal in number and similar in position to those of the Stegocephalian skull, except that the supramastoid (^squamosal) extends between the parietal and inter- calare (tabulare') to the posterior border of the cranial table; and the supraoccipital does not extend onto the superior face of the skull, except as a narrow border. The quadrate bone is directed forwards instead of posteriorly, which causes an anteroposterior abbreviation of the supratemporal and squamosal elements. The elements of the temporal roof are not exclusively tegumentary, but are identical in character with the bones of the brain case, and the sutures are visible on the under as well as the upper side." In this paper he gave figures of the skull of Chilonyx. These figures were republished several times (36, 42, 44). A comparison of Cope's figure with that worked out by the author, in collabora- tion with Dr. Broom, shows that the two interpretations do not agree. There are but two bones over the temporal region, not three; the condition is the same as in Diadectes, and Chilonyx can only be considered a very specialized genus of the same family. Cope's description of the posterior surface of the skull is erroneous, as is his figure of the quadrate region (plate viii, fig. 6, Proc. Am. Phil. Soc, vol. xxxiv). It resembles in all respects the same region in Diadectes. A single successional tooth just coming into place shows a single terminal cusp. Bolbodon tenuitectus Cope. (Plate 10, fig. l ; text fig. 33, A.) Characteristic specimen: The type, No. 4375 Am. Mus. Nat. Hist. Cope Coll. The sculpture of the skull is very much less rugose than that of Diadectes phasenltnus. The portion of the quadrate region preserved indicates that the tabulare is united with the squamosal, but as the sutures can not be made out this point is uncertain. The bone described by Cope as a turbinal is the same in position and relations as that described by Swinnerton and Howes in Sphenodon and by the author in Dime- trodon as a septo-maxillary. The bones described by Cope as palatines are the anterior ends of the prevomers. The molar teeth were apparently without cusps, * Figured in Proc. Amer. Fhiloi. Soc. toI. xiz, p. 56. 88 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA but all are badly worn and the fifth has apparently lost the apex since the original description. The tooth figured by Cope (43) is the last of the series and is of little diagnostic value, as the posterior teeth in all members of the family are of similar form. Desmatodon hollandi Case. (Plate 8, figs. 2 and 3.) Characteristic specimen: The type, No. 1938 Museum of Carnegie Institute. Aside from the teeth described as typical of this genus, there are several chevron bones belonging to an animal of larger size. Whether these belong to the genus Desmatodon is uncertain; they may indicate an animal more closely related to Diadectes, as they have the form and size of the chevrons of Diadectes phaseolinus. The largest one has a length of 51 mm. Fio. 33. A. Lateral Tiev of skull of BModon unuiuclus. X i- No. 4375 Am. Mui. n, natal; /, lachrymal: mx, maxillary; pmjr, premaxillary; ^/.prefrontal. B. Lateral view of skull of £o/ai). x}. physes. The head of a small femur is without N0.4686Am.Mu.. «,topTiew; i.UttrJyiew. well-defined articular surface. The distal end, in a second specimen, shows that the femur was long and slender without well-defined entepicondylar or ectepicondy- lar processes. There is the usual entepicondylar foramen. A fragment of a pelvis, No. 4326 Am. Mus., shows that the ischium and pubis had the primitive broad and plate-like form. There seems to have been two sacrals. The type specimen is in such poor condition that little detail can be made, but the teeth of the lower jaw show the characteristic form and permit the identification of other specimens. Pariotichus brachyops Cope. Characteristic specimen: A small skull, No, 4760, Am. Mus. Nat. Hist. The type specimen is in extremely poor condition and nothing can be made out concerning the arrangement of the bones of the skull or the condition of the surface. The maxillary teeth are fairly well preserved and from these the homotype has been identified. The type skull is similar in appearance to the small amphibian Lysoro- phus, but the teeth are totally unlike any amphibian from the Permian. On the lower surface is a single broad plate, the component elements of which can not be made out. It resembles the great parasphenoid of Lysorophus, but equally so the plate formed by the parasphenoid and basisphenoid in Gymnarthrus. The homotype is in good preservation. This shows that the skull was low and the anterior end of the muzzle blunt. The orbits are large and circular and look laterally and a little upward. There is the same arrangement of the bones of the temporal region as in the Captorhinidce; that is, there are but two bones over the temporal region. The supraoccipital plates are vertical at the back of the skull. 7 92 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA The arrangement is shown in fig. 36, C and D. The teeth are bluntly conical with no anteroposterior cutting edges. The enlarged tooth is near the anterior end of the maxillary series. There are no enlarged teeth in the lower jaw, and in neither jaw can any trace of more than one row be made, but this is inconclusive, as such teeth would be covered if present. ■pmx Fic. 36. — Parimkhus brachyops. No. 4760. Am. Mus. A. Lateral rettoration of skull, x f ■ pi"*, premazillary; mx, maxillary; n, nasal; /, lachiymal; pf, pre- frontal; j, jugal; /, frontal; po, postorbital; p, parietal; sq, squamosal; psj, prosquamosal. B. Restoration of upper surface of skull, X i- Lettering as in A. C. Left side of same specimen as shown in D. D. Lateral view of skull, xi- Lettering as in A. There is no resemblance between these skulls and those of the genus Capto- rhinus, though most of the skulls of the latter genus were originally described as Pariotichus. As they form a distinct and separate group they have been placed together in a separate family, Captorhinidce. Measurements. mm Length of the type skull 22 Width of same at back 22 Length of skull of homotype 20.5 Width at back 14 Isodectes megalops Cope. Characteristic specimen: A small skull, No. 4329 Am. Mus. Nat. Hist. Cope Coll. The skull is fairly well preserved and shows a fine reticulate sculpture. No palatine teeth can be made out and the teeth on the premaxillary and the anterior /P""' F1G.37.— /jiwfcrtejsp. A. Upper view of skull, pmx, premazillary; mx, maxillary; R, nasal ; /, frontal ; pr/, postfrontal ; pot, postorbital; ^, parietal; y, jugal; jm, squamosal; jf, prosquamosal; soc, supraoccipital plates. After Cope. B. Restoration of skull according to the author, xf This restoration shows the skull too wide, as the bones have been placed to show their full width. Lettering as in previous 6gures. C. Lower jaw, showing numerous teeth. X f . part of the maxillary are more sharply conical than those on the lower jaw. The lower jaw has a prominent coronoid process and just anterior to this the dentary is widened and there is a patch of small blunt teeth. They are partly ob.scured by the matrix, so that the exact position can not be made out, but they seem to be irreg- ularly arranged; in the anterior portion of the jaw is a single row of teeth. The ■pm MORPHOLOGICAL REVISION 93 appearance of the teeth does not warrant the description given by Cope in his ana- lytical table of the genera of the Captorhinidce (Pariotichida:). He says the palatal and splenial teeth are compressed and that the jaw teeth are equal and acute. No splenial or palatine teeth can be seen and the condition of the specimen does not show that the jaw teeth are equal; there was at least one elongated tooth in the anterior part of the maxillary series. Genus CAPTORHINUS Cope. (Plate u, figs. 1. 2, 3.) Characteristic specimens: Nos. 4334, 4328, 4424, all Am. Mus. Nat. Hist. Cope Coll.; No. 642, University of Chicago. The following description of the genus is based on all the specimens, as the specific d-ir • J .. ^ J L f Fig. 58. — Captorhinui atuti. X i. No. 4-114 Am. Mus. ifferences are mmor and, as stated before, «,Low« view of skuii; i.iowerjaw. The posterior even of doubtful value in one or two cases. The best-preserved specimen of the skull is p»'»"nei pf.pterygoia. that described by Cope as Pariotichus aguti. No. 4334 Am. Mus. This has also the clavicles and interclavicle, the humerus of the right side, and the first few vertebras. The general shape of the skull, as described by Cope, is elongate, flat on the top, with a decurved snout and a wide temporal region. Premaxillaries: These are small and hardly appear on the upper surface of the skull; each one carries four teeth. The median pair is the largest, the others dimin- ishing rapidly and regularly to the maxillary-premaxillary suture. /rf, Fio. 39. — Caftorkinat anguniceps. X ♦■ No. 4457 Am. Mus. a. Upper Ti'ew of tlnill. n, nasal; /ilachrymal; f»/,'pottf rental; f/, prefrontal; ^«, pottorbital; /, frontal; /.jugal; tq, iquamotal; p, parietal; to, aupraoccipital plate; t, tabulare. 4. Lateral riew of tame specimen ibown in a. c. Posterior surface of skull, f, parietal; I, tabulare; », wprmoccipital plate; i«', nipraocdpiut; tx», exoccipital; fy, quadratojugal; if , squamosal; ^.pterygoid. The nasals are large bones reaching back nearly to the anterior edge of the orbit and forming the inner edge of the nares. The lachrymals form the anterior border of the orbit and reach forward to the nares, forming its posterior border. The prefrontals form the upper anterior border of the orbit and lie between 94 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA frontals, nasals, and lachrymals. They meet, or very nearly meet, the postfrontais behind, so that the frontals take little if any part in the upper edge of the orbit. The frontals reach nearly or quite from orbit to orbit and extend an equal distance anterior and posterior to them. This portion of the skull is flat or slightly concave. The parietals are wide, extending beyond the frontals; the parietal foramen lies in the anterior third. The posterior edge of the parietal is separated from the posterior border of the skull by the upper edge of the vertical supraoccipital plates. The postfrontais are small triangular bones, forming the posterior half of the upper edge of the orbits and a part of the posterior edge. The postorbitals are nearly square; they form the greater portion of the pos- terior edge of the orbit. The jugal is elongate, extending from the anterior edge of the orbit almost to the posterior end of the skull. It is quite high in the middle, and forms with the postorbital the posterior rim of the orbit. The squamosals: On either side of the parietal are two bones which form the posterior part of the temporal roof. The upper of these, occupying the position of the squamosal, is rather longer than broad and extends as far forwards as the parie- Fio. 40. — d. Upper view of skuU of Cd^isrAinuj iia/i>mi/i. x J. N0.4338 Am. Mus. Lettering at in fig. 39. h. Upper view of skull of C. aguli. X J. No. 4334 Am. Mus. f. Upper Tiew of skull of C.fljufi. X j. No. 4338 Am. Mus. tal foramen. Below this is a larger bone which articulates with the postfrontal, postorbital, and jugal; its posterior edge forms the edge of the skull and covers the quadrate; it is regarded as the prosquamosal for the following reasons: The posterior surface (fig. 39, c) of the skull is formed above by a pair of plates on either side, lying at right angles to the bones of the surface. The inner bones are the supraoccipital plates; they meet in the median line and extend downward, probably forming the upper edge of the foramen magnum. The outer end termin- ates in a point which is wedged in between the squamosal and the second plate on the posterior surface. This plate is abruptly wider than the supraoccipital and extends down to the posterior angle of the skull, completely covering the quadrate behind. Between the exoccipital and the second plates on each side is the large posttemporal fenestra. The outer pair of plates is homologous with the bone identified in the Pelycosaurs as the quadratojugal. A small triangular element lying between the supraoccipital plate, the squa- mosal, and the quadratojugal is the last trace of the tabulare, as suggested by Gope. With the recognition that the temporal region is covered in the Diadectidce, Pariotichida, and Captorhinidce by only two elements instead of three, as in the MORPHOLOGICAL REVISION 95 typical Stegocephalian skull, comes not only the recognition that these forms can not be the primitive stem groups of the reptilia but also the serious morphological question of the homology of the bones. Is the lower bone of the two covering the temporal region and connecting the quadrate with the jugal, the quadratojugal of higher Reptilia or is it the prosquamosal ? In Dimetrodon there is a single plate on the posterior side of the quadrate, connecting with the postorbital above and partially separated from the quadrate below by a quadrate foramen. This bone I have called the quadratojugal, and the bone which connects it with the jugal I have des- ignated as the prosquamosal (16). This nomenclature is quite different from that usually accepted and several objections have been urged against it. Notably, that the paroccipital (opisthotic) comes in contact with the bone called quadratojugal, which is not common among recent reptiles, and that the second bone should not be called prosquamosal, because the name quadratojugal has commonly been applied to the element connecting the quadrate with the j'ugal. These objections have been partially replied to and the arguments, somewhat amplified, are repeated here. In the first place it must be clearly recognized that: (i) The Rhyncocephalian skull can not be regarded as a stem form from which all other reptilian two-arched types were derived; (2) the Rhyncocephalian skull can not be derived simply and directly from the Cotylosaurian skull; (3) the Cotylosaurian skull can not be regarded as the single primitive type of reptilian skull. If we free our minds of these conceptions, so long dominant in the theory of the development of the reptiles, the questions are less difficult. The first objection to designating as the quadratojugal the element which covers the quadrate posteriorly and is separated from it in the Pelycosaurs and Dia- dectida by a quadrate foramen, is that it comes in contact with the paroccipital in Labtdosaurus and probably in Captorhinus, Diadectes, and the Pelycosauria also. This objection is not vital, for such a condition occurs in the dinosaurs Allosaurus and Tyranosaurus, where the element (quadratojugal) comes directly in contact with the jugal anteriorly and is unquestionably a quadratojugal; in other respects it is almost exactly the same as in the Pelycosaurs and morphologically the same as in Captorhinus, with the possible exception of the lack of a quadrate foramen in that genus. It will be seen that the bones on the posterior surface of the skull in Cap- torhinus and Labidosaurus have essentially the same arrangement zs in Dimetrodon; in the latter genus the cartilaginous supraoccipital has developed, and the need for the dermal supraoccipital plates having passed they have disappeared. This process can be seen in Labtdosaurus^ where both the cartilaginous supraoccipital bone and the dermal supraoccipital plates are present. When the supraoccipital plates disappeared the parietal became the posterior bone on the upper surface of the skull and the squamosals became the posterior elements on the sides of the skull; the tabulate is just disappearing in Captorhinus and is completely lost in Labidosaurus, the Pelycosaurs, and the Diadectida: (?). The squamosals would now have the same relation to the upper end of the bones lying on the posterior face of the quadrate that the supraoccipital plates did in the Cotylosauria. There is no inherent improbability that the element connecting the quadrate with the jugal is the prosquamosal (supratemporal); indeed if the arguments offered above have weight, it must be by exclusion. Other facts, however, may be cited in favor of this idea. The temporal region in the Stegocephalia is covered by the parietal, squamosal, prosquamosal, quadratojugal, and jugal. The prosquamo- sal is commonly the largest element of the temporal region; it articulates with the postorbital anteriorly below, and in many forms, as Branchiosaurus, etc., pos- % A REVISION OF THE C0TYL08AURIA OF NORTH AMERICA teriorly, with the quadratojugal; it overlies the quadrate. The quadratojugal lies on the outer side of the quadrate and frequently extends up behind it; the portion which extends up behind the quadrate articulates with the posterior edge of the prosquamosal. This is exactly the relation of the outer pair of posterior elements in Captorhinus and the Pelycosaurta. if we assume that this element covering the posterior and outer surface of the quadrate in Captorhinus, Diadectes, and the Pelycosaurta, and separated from the quadiate by a foramen, is, in the last two, the quadratojugal, then we have in the temporal region the full number of bones of the Stegocephalian skull; this bone is in many forms, where it articulates directly with the jugal (Rhyncocephalia, TherofKidus Dinosaurs, and Phytosaurs), unhesitatingly called the quadratojugal. If, on the other hand, we assume this bone to be a new element and the bone anterior to it, in Pelycosaurs and Cotylosaurs, to be the quadratojugal, the skulls are radically different from the Stegocephalian skulls, having one more element on the posterior surface of the skull and one less in the temporal region. The condition of the Pelycosaurian skull gives a hint as to the condition of the skull oi Sphenodon. Baur claimed that in Sphenodon the squamosal and prosqua- mosal had united in a single element, but Swinnerton and Howse found no trace of any division of this element in even the youngest embryos. Is it not just as probable that the prosquamosal dropped down to the lower edge of the skull and formed the connecting link between the jugal and quadratojugal as that it rose and fused with the squamosal ? In Paleohatterta the jugal joins the quadrate direct,* but the squamosal (prosquamosal .?) projects down nearly between them. The quadratojugal, if present, was on the back of the skull. As the Cotylosauria can no longer be considered as the primitive reptilian type, and as the Rhyncocephalia can no longer be considered as derived from them by the simple development of openings, the necessity of finding a prosquamosal bone in the skull of the Rhyncocephalia has passed. The more definitely the anatomy of the primitive reptiles is known, the more apparent it becomes that the theory which places the Rhyncocephalia as a central type directly derived from the Cotylosauria and giving rise to two main branches of Reptilia is inadequate and must undergo a serious re-examination. The maxillary does not have a great vertical ex- tent, in any place, and beneath the orbit it is very slen- der. Thirteen bluntly conical teeth may be counted in the outer row, of which the fourth is the largest. Just posterior to the enlarged tooth the alveolar edge widens and there are three rows of irregularly placed teeth, the inner is the shorter and the outer the longer, so arranged that the whole patch is slightly crescent- shaped. These teeth are frequently so worn that they F10.41.— Lower view of skuU of c.i»/»- ' „ , lilt """■ X I- No. 4338 Am. Mm. appear as nat-topped pegs rather than as blunt cones. The septomaxillary bones (turbinate bones of Cope) are small elements appear- ing at the surface in the lower inner corner of the nares. The lower surface of the skull: The prevomers are long and slender, meeting in the median line and inclosing anteriorly the posterior ends of the premaxillaries; * Crcdner, ZeitKh. dcutich. geol. Gctell. Jahrg. 1888, 3, 546. MORPHOLOGICAL REVISION 97 posteriorly they diverge and receive between them the anterior ends of the ptery- goids. There is no trace of teeth on the prevomers. On either side are the elongate, oval openings of the posterior nares. The palatines lie in the normal position, but the sutures can not be clearly made out; the posterior end seems to be marked by a suture extending inward and backward from a point about opposite the middle of the orbit. A short row of small teeth extending outward and forward from the median vacuity seems to be confined to the palatine. The pterygoids have the usual tripartite form. The posterior process is a thin, nearly vertical, plate extending back to the quadrate and is applied to its inner surface. A strong basisphenoid process joins the basipterygoid process of the basi- sphenoid. In the type specimen of C. aguti the palate has been very slightly crushed together from the sides, so that the basisphenoid processes lie between the basi- pterygoid processes of the basisphenoid and the interpterygoid vacuity is narrowed. This may also account for the loss of the parasphenoid rostrum in this specimen. The external processes of the pterygoid extend out to the maxillary and there is no trace of an ectopterygoid bone. The posterior edge of the external process is prom- inent and the outer end is lower and presents a terminal face to the lower jaw, as in the Crocodiha, Sphenodon, and the Pelycosauria. The outer portion of this process supported a small cluster of minute teeth. The anterior processes are long and slender and extend far forward between the palatines and prevomers. The inner edges anterior to the basisphenoid processes are concave and surround a considerable interpterygoid vacuity; opposite the anterior end of the orbit the inner edges of the pterygoids come in contact. From a point opposite the palatine suture the inner edge of the pterygoid supports a single row of small teeth. The basisphenoid is exceptionally elongate, with a deep groove on the ventral surface. The presence of foramina for the internal carotid arteries can not be made out. The paroccipital is distinct and extends out to the quadrate; as in Lahidosaurus, it comes in contact with the outer of the two vertical plates on the posterior surface of the skull, the quadratojugal. The lower jaw shows the angular, surangular, splenial, and dentary; the other bones are not visible in any of the specimens. The dentary supports a cluster of teeth arranged in three irregular rows. The teeth are obtusely conical, as in the upper jaw. The anterior teeth are concealed by the overhanging maxillary in the type specimen of C aguti, but in others it is seen that the first three were consid- erably larger than the others. The third is especially large and fits into the notch formed on the upper series by the reduction of the posterior premaxillaries and the anterior maxillaries. The splenial passes forward and takes a strong part in the symphysis. The angular and surangular extend back of the articular region and form a strong pointed projection at the rear of the jaw. The interclavicle has a broad rhomboid head with a slender posterior prolonga- tion; the end of this is broken away, so that it is impossible to give the exact length. The clavicles have flat anterior ends lying upon the interclavicle and expanded parallel to it; the distal ends are expanded, but at a right angle to the proximal ends, so that while the proximal end was horizontal the distal end was vertical. The scapula have not been made out sufficiently to give a figure. Williston (67) in his description of Captorhinus isolomus (P. laticeps) speaks of the shoulder girdle as follows: "It is very certain that the girdle was attached immediately back of the skull, the front part underlying the occipital condyle even. Its structure is almost identical with that of Lahidosaurus, as figured by me (see fig. 47, c'). I find 98 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA no indications of a cleithrum. It is very evident that the coracoids in life were in immediate contact along the median line, covered over by the prolongation of the interclavicle. The scapulae curve upward at an angle of about forty-four degrees from the plane of the coracoids. Possibly this angle has been slightly reduced by pressure, but I think not. The scapulae are directed, not backward, as has been supposed, but obliquely upward." The vertebral column: In No. 4424 American Museum there are 25 presacrals. Between the twentieth and twenty-first there is a break, as the anterior portion of the twenty-first is lost; so there is some possibility that the number was greater, but this is very improbable. Williston gives twenty-three or twenty-four in his speci- men No. 642 Univ. of Chicago, but the anterior cervicals are covered by the skull and there is a break near the sacrum, so that his number is also uncertain. The atlas is unknown. The axis does not seem to have been very different from the succeeding ver- tebrae. The spine was elongate anteroposteriorly, but not high. As all the vertebrae bear ribs and are strikingly similar in form it is impossible to divide the column into Fio. 42. — Lower jaw of C. angusticeps, X f . No. 4456Ara. Mus. tj.dentary; ip, splcnUi; sa, surangular; a, articular Fig. 43. — Capterhinut. X f ■ No. 4424 Am. Mus. a, cervical Tertebrae; b, cro$s-.section of a dorsal vertebra; e, sacral vertcbne; ^, humerus and radius; *,lcft side of pelvis. cervical, dorsal, and lumbar regions. All the vertebrae have low, rounded neural arches, with wide zygapophyses. The anteroposterior and transverse diameters of the neural arches are nearly equal. The transverse processes of the anterior verte- brae originate high up on the centrum and the side of the neural arch and stand out almost at right angles. The articular face for the rib is elongate vertically; the lower edge is attached near to the anterior edge of the centrum and is close to it, so the face slants forward and inward, as in Diadectes and Lahtdosaurus. In the pos- terior vertebrae the transverse processes are more slender and rod-like and originate high up on the centrum. The body of the centrum is contracted slightly in the middle portion, but there are no keels or ridges. Small intercentra were present throughout the column. There are two sacral vertebra. The first has a large rib expanded distally and directed straight out to the ilium. The second sacral is much smaller and its rib appears to be very largely applied to the posterior surface of the distal half of the anterior sacral rib. The caudal vertebra have more slender arches and spines than the presacrals. The first ones carry strong ribs anchylosed to the transverse process. These curved downward sharply, showing that the tail was heavy at the base. Chevrons are present in the anterior part of the column, but it is not known how far back they extended. Williston estimates twenty-five vertebrae in the tail. MORPHOLOGICAL REVISION 99 The humerus has the upper and lower ends expanded and turned almost at right angles to each other; the articular surfaces are well formed. There is a promi- nent entepicondylar process and a good-sized entepicondylar foramen. The ectepi- condylar process is extended into a distal hook. The hemispherical articular face for the radius is almost entirely on the anterior surface of the bone. The radius is slightly curved, with the upper end slightly expanded and the lower end wider and thinner. The ulna has a pronounced olecranon process. The shaft is curved, leaving a considerable space between it and the radius. Tht front foot is described by Williston (67) as follows: "Because of the compression of the middle part of the carpus in our specimen, it is impossible to be quite sure of the presence of both centralia. The radiale is much broader than long, articulating with the radius, the distalia of the second and third digits, and with one or possibly two centralia. The ulnare is a much longer bone, articulating proximally with the ulna, distally with the two inner distalia, and on the outer side with the intermedium. That there is a free intermedium here, as in Lahidosaurus, is certain, but I can not be quite sure of its extent, a part of it being apparently covered over by the radius. It articulates, as in Lahidosaurus, proximally with the ulna and distally with a centrale. Five digits are present, ^ as was to be expected. The first is represented by its meta- carpal only, either slightly removed from its articulation with the radiale, or, what is more probable, with its distale lost, or cartilaginous. In the restoration it is shown removed from the carpal bones as in the photograph of the hand also ^'^,,t!'~Afterwiiiiftoa.^ x |^ given herewith (see fig. 44). The first metacarpal is the shortest of the five, and is only moderately expanded distally. No phalanges are preserved. The second metacarpal is much longer than the first, and is much constricted in its middle. It has one short phalanx articulated with it, but little more than half the length of the metacarpal. Additional phalanges are not pre- served, but, from its size, it seems very probable that two more, and not more than two, were originally present. The third metacarpal is much like the second, but is a little longer. Two phalanges are present, the first about two-thirds the length of the metacarpal; the second fragmentary. There may have been a third ungual phalanx present. The fourth metacarpal is the longest and stoutest of all, its proximal articulation more oblique than is the case with the preceding one. The first phalanx is about three-fifths the length of the metacarpal. The second phalanx, much shorter and smaller, has at its tip a small fragment. There may have been a fourth phalanx, though there is not much probability of it. The fifth metacarpal is a little shorter than the fourth, somewhat curved and more slender. It has a small and short proximal phalanx and a fragment of a distal one at its tip. In all probability there were no more. It is, it is seen, impossible to say with certainty what the phalangeal formula of Pariotichus was, save that quite surely it was not that of the modem lizards and Sphenodon, 2, 3, 4, 5, 3. In much probability it was 2, 3. 3. 4. C3)..2-." The pelvis is quite primitive. The ischia and pubes are broad and plate-like, lying horizontally in the body and meeting in a straight symphysis, but are not suturally united (fide Williston). There is a small pubic foramen near the anterior edge of the acetabulum. The puboischiadic suture is very indefinite, but apparently lies just posterior to the pubic foramen. The ilium stands at an angle of about fifty degrees with the pubis and ischium; the crest projected strongly to the rear. 100 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA The hind limb (from Williston's description): "The /rmur and tibia resemble those of Labidosaurus. The fibula is strongly curved with a considerable expan- sion at its lower extremity, and with a small, rounded upper end. In the foot a large flat fibulare articulates with the fibula of the right side in position, closely articulating on the inner side with another large bone, evidently the united tibiale and intermedium. Four tarsal distalia are visible. The shapes of the bones distinguished agree in general so well with those of Labidosaurus, as figured by me, that I have no hesitation in giving the others from the same genus, shaded in Fio. 45. — Restoration of Caplorhinui. After Williston. the figure (fig. 45). The tibiale, however, must have been shorter than in Labido- saurus. As regards the toes, all five metatarsals are visible on one or the other side, and many of the phalanges, save those of the fifth toe. In the figure given in the restoration (fig. 45) the unshaded phalanges are given precisely in the positions they occupy with regard to the tarsus, so that the length of the toes is quite certain. Those phalanges which can not be extricated from the matrix are shaded. In all probability the phalangeal formula is like that of the front feet; certainly there can not be a greater number." The ribs: A small rib is present on the axis, and there was probably one on the atlas, but this is not known. The third cervical carries a large rib, with the proximal end broad and thin, but not divided into capitulum and tuberculum; immediately MORPHOLOGICAL REVISION 101 below the proximal end the shaft is contracted and then spreads out in a wide, flat distal end. This distal expansion is noticeable on the first four vertebrae, after which the ribs are elongate and very slender. On the fourth vertebrae anterior to the sacrum there is no face for a rib, so the last articulated rib probably occurred on the twenty-first. Abdominal ribs: Williston detected a few very slender abdominal ribs just anterior to the pelvis. They probably extended over the abdomen. Measurements. Type specimen of C. aguti, 4334 Am. Mus. mm Length of skull 67 Width across quadrates 47 Width of alveolar edge opposite center of orbit 25 Interorbital width 20 Length of ramus 61 Greatest depth of ramus II Length of humerus 34 Width of distal end of humerus .... 25.5 Specimen No. 4424 Am. Mus. Length of skull Breadth, approximate . Length of humerus Breadth proximal end Breadth distal end Length of radius . Length of pubis and ischium 70 60 355 12 15.1 19.5 35 Genus LABIDOSAURUS Cope. (Plate 12.) Characteristic specimens: Nos. 4427 and 4876 Am. Mus. Nat. Hist., Nos. 64I and 642 University of Chicago. The mounted specimen in the Alte Akademie, Munich. Labidosaurus is an abundant form in the upper part of the Texas Red Beds, but the specimens are commonly very imperfect and covered by a refractory matrix; recent discoveries, however, make the osteology of the genus fairly well known. The following description is taken from several specimens, notably from the work of Cope, Williston, Broih, and Case. The skull: The description of the skull is largely taken from Williston's recent description of specimens Nos. 641 and 642 in the University of Chicago. "The skull is remarkable for its attenuated facial region, and for the beak-like extension of the premaxillaries, terminating in the long, rake-like teeth. The nares, situated nearly at the extremity of the rostrum, are semioval in shape, directed out- ward. The face in front of the orbits is narrow, gently convex from side to side, with nearly vertical sides and a gentle longitudinal convexity in the middle. The orbits are a little longer than wide, their diameter a trifle greater than the interorbital width. Posteriorly the skull is flattened in the middle above, and greatly expanded in width, the expansion beginning near the back part of the orbits, the lateral margins curving inward at the extreme posterior part. The large pineal foramen is situated near the front part of the parietal bone, about midway between a line drawn through the hind margins of the orbits and the hind margin of the skull in the middle line. There is a pronounced emargination of the hind margin of the skull, extending the width of the parietal bones. In well-preserved specimens the markings of the surface of the skull are very distinct, consisting, for the most part, of round or oval pits forming a reticulation, but not distinctly arranged in rows. In other specimens these pits are less conspicuous, and the surface in some appears almost smooth. "The premaxillae are separated in several of the specimens in the museum. They unite broadly above with the nasals, by a rounded border in front of the middle of the nareal margins; and on the sides with the maxillae, below the nares. The two bones together present a strong anterior convexity, with the alveolar border receding. Each has three elongated, pointed, slightly recurved teeth, of which the innermost is the largest, the outermost the smallest, less than half the length of the longest In 102 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA the closed mouth these teeth, or the inner ones, protrude quite a distance below the mandible, hook-like or rake-like, as shown in plate 12, fig. 4 (of this paper). This extraordinary development of these teeth and their position, in association with the narrow, compressed facial rostrum, remind one strongly of the phytosaurs and are suggestive of like habits in the living creatures; the exhumation of burrowing inver- tebrates from the mud or sand of the shores or shallow water. The maxillae, free in one of our specimens, are rather slender bones, with their greatest width a little in advance of the orbits. They extend back, decreasing in width, to nearly opposite the posterior part of the orbits, uniting above in front with the elongated lachrymals, behind with the anterior prolongation of the jugals. "I count in different specimens seventeen teeth, not very different in size, the longest a little in front of the middle of the series, and the series separated from the outermost of the premaxillary teeth by a short diastema. The nasals form the upper side of the rostrum as far as their union with the frontals, a little in advance of the orbits, cumng a little downward on the sides back of the nares, whose upper borders, only, do they form. The prefrontals are subtriangular in shape and small; their Fig. 46. — Labidotauru!. One of the specimens on which Copt based the genus. X J. No. 4414 Am.Mus. Oy top Tiew, no sutures shown; b^ side view of a; c, diagram of top of skull showing probable position of sutures. Lettering as usual. inner sutures begin a little beyond the middle of the upper orbital margin and are parallel with each other, extending a little beyond the end of the frontal bones. The lachrymals are large bones, united broadly with the nasals, anterior to the prefront- als, and with more than half the length of the maxillae below. They form the posterior boundary of the nares and the larger part of the anterior border of the orbits. The precise boundary between the nasals and lachrymals may be somewhat indefinite; the sutural line given is that in which four skulls seem to agree. The frontal bones have nearly parallel sides, extending posteriorly a little beyond the hind margins of the orbits, joining the parietals in a transverse serrate suture, which appears on the under side somewhat in advance of the line above. The frontals form but a small part of the upper orbital margin. The postfrontals are also small, forming the posterior upper margin of the orbit, and leaving but a small space of frontal margin between them and the prefrontals. The postorbitals are larger than the postfrontals, and also extend a little further back of the frontal suture. They form most of the hind border of the orbits, articulating with the squamosal behind and the jugal below. The jugals begin a little in front of the middle of the orbit in an acute point between the lachrymals and the maxilla. They are broader just behind the orbit, where they articulate with the postorbitals above and the squamosal MORPHOLOGICAL REVISION 103 behind. Below the latter they extend as a rather narrow prolongation to or nearly to the hind angle of the skull, and to the outer extremity of the ' epiotic ' bones. In the skull figured by Case and myself these posterior prolongations appear to be suturally separated from the broader part of the jugals in advance. A careful examination of other specimens, however, reveals no suture here and leads me to the belief that the supposed suture is merely a fracture in the same place on each side, due doubtless to the fact of the subangular narrowing of the jugal at this place. If there be a distinct bone here I suppose that it must be the real quadratojugal notwithstanding it has no articulation with the quadrate. All the sutures I have so far described, save perhaps that between the nasal and lachrymal, and that between the postorbital and jugal, are decisively and clearly indicated in the dif- ferent specimens, some of them conspicuously so, and they, moreover, agree in the different specimens, as long and patient examinations and careful measurements testify. "Cope's determinations of the cranial elements in Pariotichus and both Case's and my own in the small skull of Labidosaurus recognize another suture dividing the so-called squamosal into two distinct elements, though we do not agree in the position of this suture. In the Labidosaurus skull figured by myself there does appear to be a divisional line, indistinctly shown and agreeing on the two sides pretty well. Unfortunately, in a half-dozen other specimens showing this part of the cranial wall, some of them in the most perfect condition both above and below, I can find no trace of a divisional suture, even under the most careful examination with a lens. I am satisfied that there is none; that there is but a single bone here and not two, and this conclusion was reached before I perceived its significance in comparison with the skull of Dimetrodon. This large, flat and thin, or gently con- vex bone unites on its inner side with the parietal, on the front side with the post- frontal and postorbital, and on the lower or outer side by a very squamous and loose suture with the posterior prolongation of the jugal. This is precisely the arrange- ment of these bones in Dimetrodon, and I am satisfied that the elements are mor- phologically identical. The chief difl^erence between Labidosaurus and Dimetrodon consists in the rather large vacuity of the latter piercing what otherwise would be the squamosal, jugal, and postorbital bones. For the present I accept Case's determina- tion of the squamosal element as the prosquamosal, but I feel far less assured of its homology than I did formerly, though I doubt not that it corresponds quite with the element in the ichthyosaurs originally named prosquamosal by Owen. "On the posterior or occipital side there are two cranial roof bones on each side, clearly and positively shown in all our specimens, one bordering the hind margin of the parietal, the other the squamosal, and called by Cope respectively the supra- occipital and the tabulate — that is, the so-called epiotic of authors. They differ from the bones of the upper surface of the skull in lacking the superficial markings or pittings, and are suturally united with the superior bones at an angle of nearly ninety degrees. The superior or inner of these two pairs of bones, those bordering the parietals, the supraoccipitals of Cope, are the narrower of the two. Their inner ends are curved downward slightly, with an angular interval between them, into which fitted the small spine of the real supraoccipital described further on. It has long been believed that the so-called supraoccipital of the Stegocephala and of those reptiles in which a like bone is believed to occur does not correspond to the true supraoccipital of the higher reptiles and mammals. They are clearly membrane bones, and have been called the postparietals by Broom. That they are not the real supraoccipitals is very evident In this specimen, in which a large and well-defined supraoccipital is found quite dissociated from the membrane bones of the cranial 104 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA wall. These bones unite at their outer end with the upper part of the so-called epiotic; the lower, thin and somewhat concave border is free. The epiotics are broader and longer than this postparietal, with nearly parallel sides, the lower margin thinned and free and concave in outline, the upper uniting by suture with the squamosal at the angle of the skull. The inner end, which is truncate, unites above with the 'postparietal'; below it presents an oblique articular facet for union with the extremity of the paroccipital. The outer extremity is rounded below, and extends to the angle of the skull, articulating apparently with the posterior end of the jugal. On its inner surface near the roof it articulates for a large part of its extent with the hind border of the quadrate. Further observations on the homol- ogies of this remarkable bone will be given later. "The more complete of the two larger skulls has the palatal and basicranial regions in excellent preservation, and but little distorted. Just back of the trans- verse bones a recent fracture through the narrowest parts of the free pterygoids has permitted the removal of the posterior portion and its complete separation from the incrusting matrix, both above and below, enabling one for almost the first time to obtain a clear conception of the cranial bones and their relations to each other. Very remarkable is the fact that all this portion has no sutural connection with the cranial walls, the suture between the quadrate and the epiotic being the only one, indirectly connecting the vertical elements with the superior membrane bones. This will readily account for the fact so often observed, of the loss of the basioc- cipital and basisphenoid from the remainder of the skull, a loss which, erroneously interpreted, induced Cope to give the name Cotylosauria to the whole group. Above, in the middle, the 'postparietals' merely touch the supraoccipital, while the epiptery- goids further in advance touch the parietals in a mere rounded point. "The quadrate bone of the left side in this specimen lacks its articular head, which had been, unfortunately, broken off with a part of the articular and lost before the discovery of the specimen. The remainder of the quadrate, however, is quite in position, overlapping the pterygoids, and is complete. On the right side the quadrate, nearly complete, has been entirely separated from its articular relations. The vomers, anterior part of the pterygoids, the palatines and the transverse bones are all in their normal positions. The nares, situated far in front, probably directly below the external orifices, are concealed by the mandibles, which are closed upon the maxillae; nor is the suture distinguishing the vomers from the posterior elements distinguishable. The narrow pterygo-palatine shelf on each side shows, on the upper side at least, a suture between the palatines and pterygoids for a portion of the dis- tance, though I can make out no suture separating the transverse bones, though such doubtless existed. The transverse bones are stout, forming a strong declivity from the plane of the palatines, and they abut massively against the mandibles at least as far as their middle. In the middle, between the pterygoids, opposite and in front of the transverse bones, there is a large ovate interpterygoidal space, in front of which the two pterygoids approach each other closely, though not touching. Possibly in the living skull they actually met in the middle. In front of the basisphenoid the pterygoids curve inward so that they meet in the middle behind, leaving no space for a presphenoid or parasphenoid, which is certainly wanting in this, specimen at least, though distinctly present in a smaller skull, and recognized by Broili in this species. The pterygoids unite firmly with the basisphenoid by this inner sphenoid process. Along the margin of the interpterygoidal opening, for nearly its whole extent, there is a row, possibly double in front, of small tubercular teeth; a patch of similar teeth is also present in front of the transverse declivity of the palatines, and yet another patch on the summit of each transverse bone. MORPHOLOGICAL REVISION 105 "The posterior prolongations or quadrate processes of the pterygoids, arising just back of the transverse bones from the base of the stout sphenoid processes, are long, thin, divergent, oblique plates of bone, extending back nearly to the hind margin of the skull, articulating broadly but loosely with the plate of the quadrate as shown by the dotted lines in figure 3, plate 12 (of this paper). The inner border nearly touches the sides of the basisphenoid; the lower, thin and nearly straight border is continued to near the articular extremity of the quadrate. The basisphe- noid is narrow in front, gradually widened behind, grooved in the middle, shallower in front, more deeply behind, where it is bordered on each side by a descending process which terminates in a free, thin margin underhanging a fossa that opens backward. I can not distinguish with certainty the sutural division between the basisphenoid and basioccipital, though it seems to be wholly back of the lateral pro- cesses, since in another skull, in which the basioccipital has been dislodged, the division has been made back of these processes. On either side of the basisphenoid, or the conjoined basisphenoid and basioccipital, an elongate, cylindrical or oval rod is given off, which is directed downward, outward, and backward, lying closely under the posterior end of the pterygoid plate, and reaching nearly or quite to the head of the quadrate. This process, clearly the stapes, seems to be suturally united with the basisphenoid, as indicated in figure i, plate 12 (of this paper). The position of the bone in the specimen seems to be quite normal and undistorted, and the bone is nearly complete, though possibly the extreme end has been broken away; it seems to be perforated proximally by a small foramen. The shape, form, and relations of the basisphenoid, stapes, and pterygoids may be compared with the author's figure of the same parts in the remarkable rhachitomous amphibian recently described by myself.* "The basioccipital bone, limited as I believe it to be in front, is small and is clearly distinguishable from the exoccipitals. Its condyle is convex, oval from side to side, somewhat pitted in its middle, and seems to be wholly composed of the basioccipital. The exoccipitals are small, apparently taking no part in the condyle. The suture limiting them from the basioccipital is clearly seen at the sides below and joining the margin of the foramen immediately at the side of the condylar surface above. The suture separating it from the paroccipital passes through the jugular foramen, thence directly upward and forward. The exoccipitals join the supra- occipital by a transverse suture a little below the summit of the foramen magnum. The foramen magnum is heart-shaped, about eight millimeters in its greater diameter. The paroccipitals or opisthotics are distinct elements, the distinguishing suture very clearly indicated, as already stated. They are stout at their base, and are turned outward and backward to end in a short cylindrical rod lying under the prox- imal posterior end of the quadrate and articulating at the extremity with the facet already described on the lower part of the inner end of the 'epiotic' This articular arrangement is the normal one of the opisthotic with the epiotic in the Stegocephala. Chiefly because of this fact I am loath to identify the bone with the quadratojugal, to say nothing of the anomalous position of the bone for a quadratojugal. Anteriorly the suture separating the paroccipital from the supraoccipital passes nearly directly forward to the outer side of the posterior lateral projections of the supraoccipitals where the dividing suture turns inward. Of the suture separating the prootics I am less certain, though it seems to be quite apparent in the position I have figured it in the drawing. The supraoccipital is a large element, when seen from above having a marvelous resemblance to the arch of a dorsal vertebra. A small dorsal * Trtmatopt millerl, Journal of Geology, vol. xvii, p. 6'i6, 1909. 106 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA spine in the middle posteriorly is intercalated in the angle between the inner ends of the postparietals, but there is no sutural attachment. Anteriorly the two sides of the supraoccipital diverge in the form of zygapophyses, with an emargination between them exposing the cerebral cavity. From the median posterior spine a ridge runs outwards to each 'zygapophysis'. In front of each lateral projection, the prootic, distinguished suturally, descends in a rounded margin to form the optic notch. In front of these optic notches there is, on either side, a thin, vertical plate, attached either to the prootic or basisphenoid below the meeting in the middle above, leaving an opening of rather small size between them. The upper end of these plates is frac- tured, but it is very evident that, in position, relations, and shape they agree quite well with similar bones bounding the cerebral cavity in most lizards, a small bone, usually lost in the macerated skull, whose homology is not well understood. Since their position is in front of the optic nerve it would seem to preclude the possibility of their being alisphenoids. These elements in the Mosasaurs I have identified as orbitosphenoids (see University of Kansas Geological Survey, vol. iv, pi. xxix, f. 5; Kans. Univ. Quarterly, vol. xi, p. 249), but neither identification is quite satisfactory. "The upper oblique surface of the pterygoid wings is concealed posteriorly by the quadrates. In front of the quadrates, and occupying nearly the whole extent of their margin and the upper half of their externo-superior surface, are the elongated and oval epipterygoids. They continue the acclivity of the pterygoid wings on the outer side a little more steeply, ending in an obtuse point a little back of the orbitosphenoid plates, which touches, but is not suturally united with, the parietals above. These epipterygoids are broader in front, where they come in contact with each other over the pterygoids. The quadrates in the larger specimens, and also in one of the smaller, are preserved nearly or quite intact, and in their natural re- lations. They unite with four bones only, the pterygoids by a very broad and loose union, as shown in fig. 2, plate 12 (of this paper), with the outer ends of the paroc- cipitals, as also shown by the dotted lines in the same figure and in fig. 3, plate 12 (of this paper), and by their posterior everted articular margin with the outer extremity of the postparietals and much more extensively with the ' epiotics ' near the cranial wall. The thin, expanded proximal plate of the quadrate, as shown in fig. 3, plate 12 (of this paper), narrows into a distinct neck, chiefly by a groove which winds from the under side about the hind margin a little above the articular extremity. The notch thus formed is clearly the auditory notch, corresponding to the notch of foramen in the quadrate of the Mosasaurs and lizards; and possibly also it corresponds with the so-called quadrate foramen of the Pelycosauria. Doubt- less the Cotylosaurta had a small external ear situated nearly as it is in the lizards, above the angle of the mandible. The articular surface of the quadrate for the mandible is oblique to the plane of the bone, so as to look more nearly downward in the normal position of the quadrate. Its outer side projects into a rather narrow process, but does not touch, much less articulate with, the roof bones. "The mandibles, in comparison with the skull, are stout and heavy bones, and amply attest the predaceous habits of the animals. They are slightly expanded in front, where they meet in a short symphysis, heaviest and stoutest just back of the orbits and broadest also here. They are nearly straight or gently incui^ved anteriorly turned inwards in a broad cui^ve behind. The splenial bones unite in a median symphysis in front and extend back nearly to the articular, leaving a broad, elongate open cavity on the inner side from immediately back of the orbits. They also form a part of the lower margin of the mandible, visible from below as far back as the middle of the orbits, having between them and the hinder end of the dentary, an elongate and acute projection of the angular. The suture between the angular and MORPHOLOGICAL REVISION 107 the articular continues the curve of the inner border of the mandible to the outer side of the extreme posterior end of the angular process. The suture between the angular and the surangular passes forward nearly midway of the mandible, and nearly parallel with the upper border in the closed jaws, to the hind end of the den- tary, that is to nearly opposite the posterior end of the orbits. The thin ascending plate of the surangular reaches at the summit nearly as high as the lower margin of the orbits on the inner side of the temporal roof. Over the summit the slender posterior end of the coronoid is visible in the closed jaws, but its anterior part is concealed by the transverse bones. The articular is a short bone, turned inward, with a thin inner margin. It is apparently continued forward as a slender prolonga- tion above the margin of the splenial or angular and forming the lower border of the mandibular cavity, to a slender, acute point nearly as far as the hind end of the mandibular tooth series. Whether or not it is separated from the articular as a distinct bone, the prearticular, or indeed of its precise relations I will not be sure. Sixteen teeth I count in the mandibular series in three different skulls. They resem- ble the maxillary teeth, but are somewhat smaller. The first or second is distinctly larger than the following ones. "Perhaps nothing is more noticeable in the skull of the present reptile than the small comparative size of the brain cavity. While the skull measures over seven inches in length and five in width, the foramen magnum is of almost precisely the same size and shape as that of a small Amblyrhynchus lizard whose skull measures but sixty millimeters in length. Not only is the foramen of the same size, but the brain cavity also is only a trifle larger in Lahidosaurus. Small brain capacity is of course to be expected in this old reptile, and, moreover, the size of the brain cavity as compared with that of the skull may not be a fair criterion of the relative intelli- gence of the two animals. Nevertheless, that their intelligence was relatively much lower than that of the existing lizards can not be doubted." As shown in the discussion of the skull of Captorhinus, page 96, the bones described by Williston as epiotics can not be such, for these .bones are present as small, triangular nodules between the parietals, squamosals, and the supraoccipital plates (Williston's postparietals). The outer of the two plates on the posterior surface of the skull are, as Williston suggests, probably homologous with the bones of similar position in Dimetrodon and are most probably the quadratojugals; rea- sons have been given for not accepting Williston's objections to this homology as decisive. The vertebral column: The specimen described by Case (II) had but eighteen presacral vertebrae; Broili (T) described twenty-two in his specimen, and Williston is of the opinion that at least two must be missing from the specimen described by Case. A complete specimen. No. 4876 in the American Museum, has twenty-five. It is altogether probable that more than one species is represented in the numerous specimens, but it is impossible to determine this point. It is only certain that the genus Lahidosaurus had a maximum number of twenty-five presacral vertebrae. The atlas and axis are present in No. 4876 Am. Mus., but are obscured in part by the skull. There is a good-sized atlas centrum, but the neural arches are lost. Broili describes a keel in the lower surface of the centrum in his specimen. Evi- dence of a preatlantal intercentrum is also present. The spine of the axis is broken off and lost, but the neural arch shows it to have been quite heavy. The transverse processes are set high up on the sides of the neural arch and the face for the rib is short; there seems to be a small diapophysis present on the centrum, indicating that the rib was perhaps double-headed. The transverse process of the third vertebra has an elongate face for the wide proximal end of the single-headed rib. S 106 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA Posterior to the axis the presacral vertebrae are very similar in form. They are of the same general type found in the Diadecttda and Pareiasauridce. The centrum is notochordal with wide funnels at the anterior and posterior ends; the lower line is shortened for the accommodation of intercentra. The neural arches are low and wide and swollen, so that the upper surface looks almost hemispherical. The spines are low and short, bifurcate in the anterior vertebrae, but more posteriorly, terminat- ing bluntly as if they might have been attached to some dermal plate above. The zygapophyses are large and perfectly horizontal. There is no zygosphene or zygan- trum. The neural arch is coossified with the centrum. The transverse processes have elongate terminal faces for the single-head ribs; these are shorter than the rib heads, which were either attached to the intercentra directly or by cartilage. All the vertebrae were bound closely together by the wide overlapping of the zygapophyses and by strong ligaments lodged in a pit at the base of each neural spine behind. The transverse processes diminish in size in the posterior part of the series and the last four or five presacrals did not carry ribs. Fic. 47. — LiAidosaurus. X J. a, dorsal Tcrtebne. i, front view; 2, top view of ume vertebra. No. 4875 Am. Mui. b, rib of the anterior dorul serici. No. 4550 Am. Mus. c, shoulder girdle. CI, clavidej le, interdaTide; Sep, scapula; Co, coracoid; Pc, procoracoid. d, cervical and dorsal vertebrs. After Williston. There are two sacral vertebrae which have more elevated and slender neural arches than the presacrals; they are not united into a sacrum. The caudal vertebra have more slender neural arches, resembling in this regard the sacrals rather than the presacrals. They diminish rapidly in size and are about seventeen in number (Broili). The ribs (fig. 47, b) have expanded proximal and distal ends; the capitulum and tuberculum are not separate, with the possible exception of the axial rib, but are clearly indicated in the anterior dorsals. The rib of the third vertebra is bent at almost a right angle, but those of the posterior vertebrae are more nearly straight. The distal end is wide and spatulate. The anterior sacral rib is very large, with the distal end as wide as the centrum is long. The rib of the second sacral is much more slender than the first and its distal end underlies that of the first rib; both extend almost directly outward from the vertebrae. MORPHOLOGICAL REVISION 109 The shoulder girdle (fig. 47, c) : The interclavicle is rhomboidal with a strong posterior prolongation; the clavicles are expanded at the anterior end and overlap the interclavicle; the outer surface of the clavicles and interclavicle is not sculptured, but the edge of the latter is marked by rugose striations where it is overlapped by the clavicle. The distal end of the clavicle is striate. There is no cleithrum. The scapula is rather short and the distal is turned dorsally, almost at a right angle to the coracoidal portion. There is a good-sized coracoid which takes large part in the cotylus for the humerus and is separated from the scapula by a distinct suture. The suture between the procoracoid and scapula is less certain, but seems to have been present. There is a distinct foramen between the procoracoid and the Fig. 48. — LAiiataurus, «, abdominal ribi;i, right side of iKhium and pubis. No. 4876 Am. Mu«. c, femur. iurut. After Broili. About i natural size. and the outer side of the distal portion. On the inner side, the astragalus is closely united to, or fused with, a small centrale. Above, the astragalus and calcaneum are in close contact, but there is a distinct foramen between them. The calcaneum is flat and thin and roughly round in outline. There are five distal elements. The number of phalanges is uncertain, but it seems probable that the primi- tive number 2, 3, 4, 5, 3-4 was present. The phalanges were fairly long and heavy, indicating that the animal had a large, well-formed foot. Measurements. Specimen described by Broili — Continued, ^im Distance between nares .... 21 Distance posterior border of nares to ante- rior border of orbits 51 Length of the orbits 4 Breadth of the orbits 3 Distance between the orbits . ... 27 Distance oforbits from edge of skull . 7 Height of the skull above foramen magnum 8 No. 4883 American Museum : Length of femur 70 Width lower end of femur 35 Length of tibia 49 Length of fibula 56 No. 4876 American Museum: Length of tibia 43.5 Length of fibula 50.5 Length of tarsus and foot as laid out . 83 No. 4394 American Museum: Length of interclavicle 107 Breadth of anterior end of interclavicle 55 Length of scapula 106.5 Greatest diameter of cotylus .... 50 No. 641 University of Chicago: Greatest length of interclavicle Greatest breadth of the head of the inter- clavicle, 23.5 Anteroposterior length of scapula-coracoid 52.5 Breadth of same at humeral cotylus . 36 Length of the head on median line from posterior edge to a point opposite middle of nares 120.5 Interorbital width 26 Breadth of skull at posterior end . 127 Breadth across orbits 80 Breadth across nares (approximate) . 30 Length of lower jaw 150 Greatest length of humerus Breadth of lower end of humerus Breadth of lower end of femur . Specimen described by Broili: Total length of skull in the middle line . Breadth of skull near posterior end . Breadth of skull at posterior end oforbits, Breadth of skull at anterior end oforbits, Breadth of skull at end of snout. Length of anterior nares 18 Breadth of anterior nares I 66 30 26.5 185- .65 13 7 2 112 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA Labidosaurus was a low, squat creature with relative large feet and a powerful tail. It probably rested normally with the belly on the ground and only occasion- ally assumed the more erect position shown in the accompanying reconstruction (fig. 50) copied from Broili. Williston believes that the powerful hooked incisor teeth may have been used to drag small invertebrates from crannies in the rock or to detach closely clinging limpet-like forms. Family SEYMOURIDAE. Genus CONODECTES Cope. Conodectes favosus Cope. Characteristic specimen: The type. No. 4342 Am. Mus. Nat. Hist. Cope Coll. Conodectes was described by Cope with Otoccelus, and the two were placed in the family Otoccelidce, but as Octocaelus is an amphibian the name of genus and family are transferred to that class. Conodectes is represented by a single poorly preserved skull, but as it is reptilian and resembles Seyniouria Broili very closely in some respects it is united with that genus in the family Seymourida. The skull is in such wretched condition that the sutures can not be made and it has been largely restored in plaster by Cope. The otic region is peculiar in the elongation of the epiotic notch at the anterior end. This is continued inward and downward until it terminates in a deep pit. On the lower surface the broad plates of the prevomers, palatines, and pterygoids can be made out. The latter approach each other in the median line, and this is the chief reason why the animal is regarded as a reptile. There is no trace of teeth on these bones, but there may have been such in life. The maxillary teeth were uniform in size, but are too poorly preserved to show more than their form. Broken teeth do not show any radiation of the dentine from a pulp cavity. The parasphenoid was apparently of small size. Genus SEYMOURIA Broili. Seymouria baylorensis Broili. (Plate 13.) Characteristic specimen : The type in the Museum of the Alte Akademie, Munich. The Cotylosauria can no longer be regarded as the primitive type of the reptile, as the bones of the temporal region are widely different from those of the Stegocepha- lia. Broili (5, 6) has amply demonstrated the strikingly amphibian resemblances of Seymouria, but his original belief that there were three bones in the temporal region is unfounded, and Seymouria takes its place close to Captorhtnus and Labidosaurus. The presence of an intertemporal bone places it in a distinct family. The sugges- tions, founded on Broili's belief in the presence of three bones in the temporal region, that Seymouria would perhaps turn out to be the connecting form between amphibians and reptiles, must be abandoned. Such a form when found will prob- ably be among the numerous small forms which were so abundant at the close of the Carboniferous. The holospondylus vertebrae and the small parasphenoid are the characters which proclaim its reptilian nature. The structure of the palate, shoulder-girdle, and ribs in Seymouria is similar to that of the Labidosaurus; the skull is wonderfully Stegocephalian, but the structure of the shoulder-girdle in Labidosaurus is so much like that of such Stegocephalians as Trimerorhachis that Seymouria approaches very closely to both classes. MORPHOLOGICAL REVISION 113 Family PANTYLIDAE, Genus PANTYLUS Ope. Pantylus cordatus Cope. Characteristic specimen: The type, No. 4330 and No. 4331 Am. Mus. Nat. Hist. Cope Coll. The type specimen consists of a skull with the upper portion well preserved, lacking only the bones of the temporal region, but with the course of the sutures preserved on the cast of the lower surface. The lower jaw of the right side is in place. The left jaw is broken away at the middle of the maxillary. The bones of the back of the skull and the palate are largely destroyed. . v^^-. Originally referred by Cope to the Stegocephalia (24), Pantylus was recog- nized by him as a reptile in 1882 (26). In 1892 (35) he compared Pantylus with Chilonyx, noting that it differed in the fact that the suspensorium was directed straight downward instead of forward. In the series of figures there published for the first time and several times repeated (36, 42, 44) Cope figured this animal correctly as having the full complement of bones in the temporal region, i. e., Fio. 51. — Skull erf Pantylus cardatui. X }. No. 4330 Am. Mua. M, lower view; 4, upper Tiew. squamosal, prosquamosal, jugal, and quadratojugal. The posterior portion of the prosquamosal is bent nearly at right angles and forms a portion of the vertical posterior surface of the skull. There is no trace of the tabulate; it was either absent or was reduced to small size, as in Captorhinus, and has been destroyed with the median portion of the supraoccipital in the injury to the back of the skull. The quadrate was originally completely covered, but the breaking away of the bones of the temporal region shows that its upper part was a thin plate reaching to the top of the skull and in contact with the quadratojugal, prosquamosal, and squamosal. The inner face was overlapped by the vertical posterior end of the pterygoid. On the lower surface can be seen the sphenoid processes of the pterygoids. Anterior to these the inner edges of pterygoids are concave, leaving a large interpterygoid space. The edges of this portion of the pterygoid are lined with minute teeth. This peculiar vertical termination of the posterior part of the skull extends to the posterior end of the lower jaw. On the left side the posterior portion of the maxillary is broken away, showing a closely set group of strong crushing teeth on the palate, and in specimen 4331 the posterior portion of the lower jaw shows a corresponding and opposed set. In this regard Pantylus resembles Naosaurus (EJaphosaurus); it is, however, but a devel- opment of the condition found in Captorhmus. 114 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA The maxillary and premaxillary teeth are much heavier and more blunt than in Captorhinus and exhibit nothing of the diversity shown in Edaphosaurus. The posterior portion of the maxillary is covered, and it is impossible to say whether there was more than one row of teeth or not, but it is possible that there was but one, as the function of these in Captorhinus was probably taken by the patch of blunt teeth on the palatines and pterygoids, as in Edaphosaurus. Fig. 51. — Pantylus cordatut. a, Restoration of upper nirfacc. After Cope. Lettering a< in previous figures. X }. b, Restoration of side of skull. After Cope. Lettering as in previous figures. X 4. c, Restoration of side of skull, according to the author's interpretation. X J. No. 4330 Am. Mus. d, Upper view of fragment of left lower jaw. x J. No. 4331 Am. Mus. The lower jaws, as shown in specimen No. 4331, were nearly flat on the lower surface and the inner surface was nearly vertical, so that the two surfaces met in a right angle. The patch of teeth mentioned above is arranged in seven irregular rows; the anterior edge of the patch is broken away, so its anterior extent can not be made out; the anterior part of the jaw, specimen 4330, has but a single row of teeth; a fortunate break shows that the first was small and the second abruptly larger. A small fragment of a lower jaw. No. 4445, was labeled by Cope Pantylus tristychus. It was never described and is in all probability from an old individual o{ Captorhinus. CONCLUSION. The order Cotylosauria, as defined in this paper, includes all the primitive reptiles with a complete roof over the temporal region of the skull, single-headed ribs, and the neural arches of the vertebrae broad and low, with swollen sides and short spines. It has become increasingly apparent during these studies that the order Cotylosauria, as defined by Cope, was very far from occupying the primitive position assigned to it by him. The forms on which he based the order, now confined to the suborder Diadectosauria, can only be considered as a very specialized branch of the primitive stem. The order originated as early as middle Pennsylvanian time (Eosauravus Case and Sauravus Thevinin) and spread over the world. By upper Pennsylvanian time widely different suborders were established in North America, in Pennsylva- nia (18), and perhaps Texas (17); in the Permian other suborders were established in Germany, South Africa, and Northern Russia and a little later, in the Trias, they had spread to Scotland and over Central Europe. The wide distribution of the order in middle Permian time indicates very clearly its much earlier origin, unless we resort to the improbable assumption of a diphyletic origin. It is impossible to point with any degree of confidence to the place of origin of the order. Eosauravus, from the beds of Alleghany age in Linton, Ohio, is the oldest- known reptile, but Sauravus of France is nearly as old. The Cotylosauria of North America were of Pennsylvania or lower Permian age. A consideration of the follow- ing table makes it apparent that most of those of the Old World were a little younger. Name. Loulitjr. Geological Horizon PareiasauTus South Africa Pareiasaurus Beds, Beaufort, Middle Permian. Antkodon South Africa Pareiasaurus Beds, Beaufort, Middle Permian. Propappus South Africa Endothiodon Beds, Beaufort, Upper Permian. Procolophon South Africa Procolophon Beds, Beaufort, Middle Trias. Thelegnathus South Africa Cynognathus Beds, Beaufort, Middle Trias. SauTosternon South Africa Endothiodon Beds, Beaufort, Upper Permian. PauiasauTus Russia Dwyna River, Upper Permian. Elginia Scotland Gordonia Beds, Bunter, Lower Trias. TeUrpeton Scotland Sugonolepis Beds, Keuper, Upper Trias. SclerosauTus Germany Ruhen near Basel, Upper Bunter, Lower Trias. PhanerosauTus Germany, near Zwickau . . Rothliegende, Middle Permian. Suphanospondylus Germany Rothliegende, Middle Permian. Sauravus France Upper Stephanien. This does not establish the origin of the group in North America, however, as Sauravus indicates their early presence in Europe. One thing is certain, the Coty- losauria of North America were isolated from the Old World during the Permian and developed types peculiar to the continent; whether they gained access to Europe in the Triassic is uncertain. The Pelycosauria, which developed with the Cotylo- sauria, migrated as far as Bohemia in the Permian and existed in Europe after they had died in America. This has not been shown conclusively for the Cotylosauria, though evidence of certain foreign forms brought out in this paper point to the same thing. It is possible that the group, indigenous to America, became extinct there, 115 116 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA Still it would occasion no surprise to find American Cotylosaurs in the European deposits of Permian age or younger ; for if such specialized types as Naosaurus could migrate from Texas to Bohemia, even such slow-moving forms as Diadectes and Captorhinus could do the same. As in the case of the Pelycosauria, it is probable that the Cotylosauria endured longer in the Old World than the new. They occur through the Permian and into the Triassic. Specialization did not progress so far in America as in Europe, for we have in Chilonyx only the beginning of the development of prominent tubercles and spines in the skull, such as marks the extreme types, Elginia from the Trias of Scotland and Pareiasaurus from the Upper Permian of North Russia. Moreover, there is no cenainty of any defensive dorsal armor in the American Cotylosauria, while it was well developed in the European and African forms. The peculiar development and posterior inclination of the incisor teeth in Labidosaurus and Cap- torhinus is also not found outside of North America. Broom (lOa) has recently expressed the idea that there is a distinct genetic relationship between the American and South African Permian reptiles. He con- siders that the groups had a common origin somewhere in the northern part of South America, and from there spread to North America and were there isolated, and later to South Africa across the Antarctic Continent. He says: "Taking all the facts into consideration, it seems to me probable that in Upper Carboniferous times there appeared in the northern part of South America a primi- tive land vertebrate fauna comprising, among other types, temnospondylous am- phibians, primitive Cotylosaurians, and primitive ancestral Pelycosaurs. Before the conclusion of the Carboniferous period this South American fauna invaded North America and almost immediately afterwards the northern group became isolated. The isolation continued during at least the whole of the Lower Permian time, and these isolated types became greatly specialized in their struggle with some adverse conditions. What the conditions were, we do not know; and no satisfac- tory explanation has, I think, been given of the development of the enormous spines of the vertebrae in the Pelycosaurs. Nor do we know what caused the extinction of the whole fauna about Middle Permian times, but most likely some change in climatic conditions. "In South Africa the first Karroo reptile to appear is Mesosaurus, which is found in beds a little above the Dwyka tillite. It is certainly generically similar to the Mesosaurus of Brazil and closely allied specifically This occurrence of Mesosaurus on both sides of the Atlantic, as well as a series of plants which are specifically identical in Brazil and South Africa, renders it practically certain that there was a land connection between South America and South Africa in Lower Permian times, and that animals might have migrated from what is now the one continent to the other. There is, however, no evidence that any reptiles other than Mesosaurus arrived in South Africa till some considerable time after the origin of the Permian. Perhaps the reason for this may be that about the beginning of the Permian period South Africa and probably much of South America, Australia, and India was, from some cause or other, largely covered by glaciers, and possibly for long afterwards the climate was too severe to allow the more northern or equatorial types to invade the south. In beds which are called Ecca we get the earliest immigrants — a large car- nivorous reptile called Archccosuchus, which may have been a Dinocephalian, and evidence from a tooth of a large undoubted Dinocephalian which was a herbivore. It is, however, not till Middle Permian times that the fauna becomes rich. Then CONCLUSION 117 there appear Pareiasaurians, a considerable variety of Dinocephalians, many Thero- cephalians, a few Anomodonts, the only known Dromasaurians, and a temnospon- dylous amphibian. Where this great collection of forms came from is of course unknown. They can hardly have originated in South Africa, because though the lower Permian beds are lithologically exactly similar to those of later Karroo times, they are almost entirely unfossiliferous. "It seems to me, however, probable from the general resemblance of the African fauna to the North American Permian, that both have come from the common source, which I believe must have lived in the northern part of South America. After the invasion of North America in Upper Carboniferous times, all connections between North and South America ceased for a very long period. The near relatives of the ancestors of the North American Permian forms left in South America evolved on quite other lines. For long they were probably confined to the Brazilian region owing to the cold prevailing in the South, but ultimately they spread down and across the South Atlantic into Africa, where they, for the most part, arrived during Middle Permian times. "If this conclusion be correct we may regard the American and South African Permian faunas as derived from a common origin, but having evolved in quite different directions. The American types undergo many curious specializations; the African, or more preferably the South Atlantic type, is chiefly remarkable for the great development of the limbs. The Pareiasaurians, the Dinocephalians, the Therocephalians and the Anomodonts have all developed powerful limbs, and not improbably all independently of each other." These conclusions of Broom are contrary to the opinion which has prevailed among American workers on the Permian reptiles. They have held that the Ameri- can Cotylosauria and Pelycosauria are distinct and indigenous. Broom's summary of evidence only cites as common characters the most primitive features, which all date from the time when the reptiles separated from the amphibians. Such a relationship of the two groups must be admitted, but it can only be very remote. The strikingly similar general appearance of the groups as a whole, which appeals to every observer at first glance, is very probably due to the parallel development of very plastic groups in a similar environment. Such characters as follow the lines of development in each group seem to indicate wide diff^erences. The Cotylosauria is still regarded as the most primitive order of reptiles, though far from occupying the direct relationship to the Stegocephaha formerly assumed. It is a very large and comprehensive order, of world-wide distribution, containing several highly specialized suborders. The table of comparable characters (pages 63-66) shows how widely separated were some of its members. Though some forms, as Seymouria and perhaps Stephanos pond ylus, approach very close to the Stegoce- phalia in the character of skull, they are widely separated from them in other characters. It now appears we must turn to some of the small and less well-known Cotylosauria to find the probable connecting link between the reptiles and amphib- ians. It may well be that none of the forms now known will turn out to be the connecting form, but the most hopeful path leads in the direction of some of the smaller forms, such as Gymnarthus, now placed provisionally among the amphibians. The primitive form seems to have been a small creature with a low, flat skull containing all the bones of the Stegocephalian skull and without an epiotic notch. The quadrate was covered and the parasphenoid bone was reduced to a rostrum 118 A REVISION OF THE COTYLOSAURIA OF NORTH AMERICA of the basisphenoid, but was still of good size. The vertebrae were notochordal, the neural arches were low and broad, with the zygapophysial faces horizontal and with short stout spines. This character of the neural arches of the Cotylosauria seems to be one of the most persistent features and to be peculiar to the primitive reptiles. (It occurs in the Proganosaurian Mesosaurus, which is very probably an aquatic adaptation of the Cotylosaurian type and retains many of the primitive characters.) The ribs were single-headed and attached to the transverse processes. (It is asserted by Williston and Moody that the ribs of Eosauravus are intercentral in position. This is the most puzzling thing about the specimen; if it were not for this, it would form a very satisfactory connecting link between the reptiles and amphibians as far as the posterior portion of the skeleton goes.) There were about twenty-three or twenty-four presacral vertebrae, two sacrals, and twenty or more caudals. Abdominal ribs were present. The shoulder girdle of the primitive form had the coracoid and procoracoid united with the scapula; cleithrum present. The ilium and ischium were flat and plate-like and the bones of the opposite sides met in a straight symphysis, but were not united. The articular surfaces of the limb bones were well formed. The two ends of the humerus were turned almost at a right angle to each other and there was an entepicondylar foramen. The carpus had radiale, intermedium, and ulnare, probably two centrale, and five bones in the distal row. The phalangeal formula was almost certainly 2, 3, 4, 5, 3. The tarsus had tibale, fibulare, five bones in the distal row, and a pisiform. The departure from this primitive type was: 1. The change in position of the bones over the temporal region. In some the supraoccipital plates became vertical, the quadratojugal took a position on the posterior surface of the quadrate, and the temporal region was covered by only two bones. In others the temporal region retained the three bones of the primitive cover. 2. The development of an epiotic notch and the final uncovering of the quadrate in some forms. 3. The separation of coracoid, procoracoid, and scapula. 4. The ischium and pubis became more nearly vertical and met at the symphysis in an angle. 5. The tarsal bones of the proximal row became united in a single large element. 6. The phalangeal formula became reduced in some. There is no single one of the Cotylosauria that can be considered as an ancestral form of the other reptiles. It is impossible to derive the Diapsidan and Synapsidan types from the known Cotylosaurs; perhaps some primitive form may have given rise to the single and double arched types by perforation of the roof, but the result of these studies has been to render this less probable and certainly to exclude any form yet discovered from such an ancestral position. The theory which places Sphenodon as the representative of the primitive form derived directly from the Cotylosauria is inadequate to explain the facts. REFERENCES. Only the most important references, and those of less importance but used in this text, are here given. For a full bibliography, prior to the year 1900, the reader is referred to Hay's Catalogue of the Fossil Vertebrata of North America. 1. Baur, G. On the morphology of the carpus and tarsus of vertebrates. Am. Nat., vol. xix, 1885, pp. 718-7ZO. 2. Pareiasauria Seeley (Cotylosauria Cope) from the Triassic of Germany. Science, n.s., vol. 5, 1897, pp. 720-722. 3. Bernard, Felix. Elements de Paleontologie. Paris, 1895. 4. BouLENGER, G. A. On the characters and affinities of the Triassic reptile, Telerpeton elginense. Proc. Zool. Soc., London, 1904, pp. 470-481. 5. Broili, Ferd. Permische Stegocephalen und Reptilien aus Texas. Paleontographica, Bd. LI, 1904, pp. 1-120. 6. Stammreptilien. Anat. Anzeig., Bd. 25, 1904, pp. 577-587. 7. — Ein montiertes skelet von Labidosaurus hamatus Cope, einem Cotylosaurier aus dem Perm von Texas. Zeitsch. deutsch. geol. Gesell., Bd. lx, 1908, heft i, pp. 63-67. 8. Broom, Robert. On the classification of the Theriodonts and their allies. Rept. South African Ass. Adv. Sci. 1903, pp. 286-294. 9. Preliminary notes on some new fossil reptiles collected by Mr. Alfred Brown at Aliwal North, South Africa. Rec. Albany Museum, Graham's Town, South Africa, vol. 1, 1905, pp. 269-275. 10. Contributions to South African paleontology. On the Pareiasaurian genus Propappus. Annals South African Museum, vol. iv, 1908, p. 351. 10a. A comparison of the Permian reptiles of North America with those of South Africa. Bull. Am. Mus. Nat. Hist. vol. xxviii. Art. xx, 1910, pp. 197-234. 11. Case, E. C. A redescription of Pariotichus incisivus Cope. Zool. Bull. Boston, vol. 11, 1899, pp. 231-245. 1 2. The vertebrates from the Permian bone bed of Vermilion county, 111. Journ. Geol., vol. vin, 1900, pp. 698-729. 13. The osteology of the Diadectidx and their relationship to the Chelydosauria. Journ. 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The reptilian subclasses Diapsida and Synapsida and the early history of the Diapto- sauria. Mem. Am. Mus. Nat. Hist., vol. I, 1903, pp. 451-507. 54. On the primary division of the reptilia into two subclasses, Synapsida and Diapsida. Science, N.8., vol. xvn, 1903, pp. 275-276. 55. Reclassification of the reptilia. Am. Nat., vol. xxxviii, 1904, pp. 93-115. 56. Owen, Richard. Catalogue of the fossil reptilia of South Africa in the collection of the British Museum, London, 1876. 57. Seeley, H. G. Researches on the structure, organization and classification of the fossil reptilia. Proc. Roy. Phil. Soc., vol. XLiv, 1888, p. 383 (Abstract). 58. Same. Pt. vi. On the Anomodont reptilia and their allies. Trans. Roy. Phil. Soc., vol. CLXXX, 1889, pp. 215-296. 59. Same. Pt. vii. P'urther observations on Pareiasaurus. Trans. Roy. Phil. Soc., vol. CLXXXiii, 1892, pp. 311-370. REFERENCES 121 60. Seeley, H. G. Same. Pt. ix. Sec. i. On the Therosuchia. Trans. Roy. Phil. Soc., vol. CLXXXV, 1895, P- 987- 61. Stappenbeck, Richard. Ueber Stephanospondylus n. g. und Phanerosaurus H. v. M. Zeitsch. deutsch. geol. Gesell., Bd. lvii, 1905, p. 379. 62. Thevinin, Armand. Amphibiens et reptiles du terrain houiller de France. Ann. de Paleontologie. T. I, fasc. 3, 1906, pp. 145-163. 63. Versluys, J. Ein grosses parasphenoid bei Dermochelys coriacea Linn. Zoolog. Jahrb., Bd. xxviii, 1909, pp. 283-294. 64. WiLLisTON, S. W. The temporal arches of the reptilia. Biol. Bull. vol. vii, 1904, pp. 175-192. 65. The Cotylosauria. Joum. Geol. vol. xvi, 1908, pp. 139-148. 66. "The oldest known reptile"— Isodectes punctulatus Cope. Journ. Geol. vol. xvi, pp. 395-400. 67. New or little known Permian vertebrates, Pariotichus. Biol. Bull., vol. xvii, 1909, pp. 241-255. 68. The skull of Labidosaurus. Am. Joum. Anat., vol. x, no. I, 1910, pp. 69-84. 69. ZiTTEL, H. v. Handbuch der Paleontologie. Munich and Leipzig, 1887-1890. 70. Griindzug der Paleontologie. Munchen, 1895. 71. Text book of Paleontology. Translated and edited by Chas. R. Eastman, New York, 1902. INDEX Antliodon, 54 Bathyglyptus, 32 B. theodori, 32 Bolbodon, 22 B. tenuitectus, 22, 87 Bolosauridae, 28 Bolosaurus, 29 B. striatus, 29, 89 Captorhinidx, 38 Captorhinus, 38, 93 C. angusticeps, 38 C. aguti, 41 C. isolomus, 43 C. aduncus, 44 Chilonyx, 23 C. rapidens, 24, 86 Conodectes, 52, 1 12 C. favosus, 52, 112 Cotylosauria, 10 Desmatodon, 26 D. hollandi, 26, 88 Desmospondylus, 61 D. anomalus, 61 Diadectosauria, 10 Diadectidae, 11 Diadectes, 12, 67 D. sideropelicus, 14 D. phaseolinus, 15, 68 D. molaris, 15 D. biculminatus, 17 D. fissus, 17 D. latibuccatus, 19 D. maximus, 20 Diadectoides, 26 D. cretin, 26 Diasparactus, 21 D. zenos, 21 Ectocynodon, 35 E. ordinatus, 35 Elginia, 54 Empedias, 13 E. alatus, 18 Eosauravus, 31 E. copei, 31 Helodectes, 48 H. isaaci, 48 H. paridens, 49 Hypopnous, 47 H. squaliceps, 47 Isodectes, 36 I. megalops, 36, 92 Labidosaurus, 45, loi L. hamatus, 46 L. broilii, 47 Nothodontid.T, 30 Nothodon, 30 N. lentus, 30 Pantylosauria, 58 Pantylidae, 58, 113 Pantylus, 59, 113 P. cordatus, 59, 113 P. coicodus, 60 Pareiasauria, 33 Pareiasaurus, 53 Pariotichidae, 33 Pariotichus, 34 P. brachyops, 34, 91 Phanerosaurus, 56 Procolophonia, 57 Procolophon, 57 Propappus, 54 Sauravus, 32 S. costei, 32 Sclerosaurus, 55 Seymouridje, 50, 112 Seymouria, 50, 112 S. baylorensis, 50, 112 Stephanospondylus, 56 Telerpeton, 58 Thelegnathus, 57 122 CASE— COTYLOSAURIA 2« On 1. Right half of lower jaw of D. Jissus. X 1. No. 4348 Am. Mus. 2. Fragment of maxillary of Z>. >ii«i. XI. No. 4348 Am. Mus. 2a, Lateral view of tooth from same specimen. 3. An incisor tooth of Diadectes sp. XI. 4. Diadectes biculminatus. X 1. 5. Maxillary teeth of D. molaris. X 1. No. 4350 Am. Mus. 5a, Lateral view of tooth from same specimen. 6. Right maxillary of /?.//!aiifo/!««i. XI. No. 4349 Am. Mus. 6a, Lateral view of tooth from same specimen. CASE— COTYLOSAURIA Skull of I), phaseolinus. X %. No. 4839 Am. Mus. 1, lateral view; 2, upper view. CASE— COTYLOSAURIA 1. Posterior view of skull of D. phaseolinus. X %. No. 4839 Am. Mus. 2. Inferior view of skull of D. phaseolinus. X %. No. 4839 Am. Mus. CASE— COTYLOSAURIA rjS^r^ 1. Upper view of skull of Diadectes sp. X %. No. 4352 Am. Mus. 2. Lower jaw of D. phaseolinus. X %. No. 4684 Am. Mus. 3. Seven dorsal and sacral vertebrae of Diadectes sp. showing hypfjsphene and hypantrum articulation. X 9io. No. 4354 Am. Mus. CASE— COTYLOSAURIA 1. Scapula and cleithrum of a large /J/aaV-f/fi, left side. XX- No. 4709 Am. Mus. 2. Humerus of a large Oiadectes, left side. X %. No. 4709 Am. Mus. 3. Lower surface of interclavicle of /->/(»/aa'<'r/«. About X- No. 1077 Univ. of Chicago. 5. Photograph of skeleton of Diadectes sp., as found, showing the shortness of the neck. No. 1075 Univ. of Chicago. CASE— COTYLOSAURIA 1. Six posterior dorsals and sacrals of Z?/a/i. Kf 1. Lateral view of skull of B. lenuitectus. X %. No. 4375 Am. Mus. 2. Top view of skull of Ckilonyx. X %. No. 4357 Am. Mus. CASE— COTYLOSAURIA PLATE 11 1. Side view of skull of Captorhinus angusliceps. X 1. No. 4457 Am. Mus. 2. Lower view of skull of Captorhinus isolomus. X 1. No. 4338 Am. Mus. 3. Top view of skull of Captorhinus auguti. X 1. No. 4334 Am. Mus. 4. Posterior view of humerus of Desnwspondylus anotnalus. X %. No. 6541 Univ. of Chicago. 5. Anterior view of same. CASE— COTYLOSAURIA PLATE 12 1. hower view of skuW of Aabidosaurus haviatus , from Williston. XI. Restored from No. 641 Univ. of Chicago, s, splenial; pa, palatine; an, angular; fit, pterygoid; bs, basisphe- noid; a, articular; st, stapes; efi, quadratojugal; e^:, exoccipital;/>/, paroccipital. 2. Posterior surface of same, fifi, paroccipital; efi, quadratojugal; g, quadrate. 3. Occipital region of same, fit, pterygoid; efil, epipterygoid. 4. Lateral view of same. X 1. CASE— COTYLOSAURIA 1. Top view ofskuW of specimen of S. bayloretisis. X%. From Broili. «, nasal; /, lachrymal; ///, prefrontal; o, orbit; tn, maxillary; ptf, postfrontal;/c>, postorbital;/, jugal;/, frontal;y/, intertemporal; sg, prosquamos- al; st, squamosal; e, epiotic;/, parietal; so, supraoccipital plates. 1. Clavicles and interclavicle of Seymouria. X %. From Broili. cl, clavicle; est, interclavicle. 3. Posterior view of skull of .Siryw/oaWa. X %. From Broili. ^, tabulare; io, supraoccipital plates; fjr, exoccipit- al; _/>«, foramen magnum;//, pterygoid; c, condyle; />, paroccipital; m, mandible. 4. Skull and anterior vertebrae of .Si»>'>«o«r/a. X %. From Broili. Letters as in fig. 1. 5. Lower surface of skull of ^yw/owr/a. X. %. From Broili. /i, parasphenoid; d/i, basisphenoid; At>, basioc- cipital; c, condyle; pt, pterygoid; p, paroccipital; d, remains of small teeth. ^ S999