PERMIAN VERTEBRATES 7 11 



The articulations for the ribs are separate in the cervical region, and become 

 more and more closely united posteriorly. The resemblance between D. 

 salamandroides and D. magnicornis is very striking, almost the only observ- 

 able difference being in the size, the latter being from five to six times the 

 size of the former. This statement is limited to the vertebral column, as the 

 skull of the Illinois species is unknown. 



In the Proceedings of the Am. Phil. Soc, 1882, p. 452 (Pal. Bull., No. 

 35), Cope gives a history of the classification of Diplocaulus and a summary 

 of the characters of the genus as derived from specimens from the Permian 

 of Texas. 



[Nos. 6513, 6514, 6515, and 6516.] 



Clepsydrops colletii Cope. Plate II, Figs, la, lb, ic, 2a, 2b, $a, -$b. 

 Clepsydrops colletii Cope, 1875, Proc. Phil. Acad. Sc., p. 407. 

 Clepsydrops colletii Cope, 1877, Proc. Am. Phil. Soc, p. 62. 



This genus was based on a series of vertebrae supposed to represent 

 the cervical caudal and dorsal regions. With them were associated other 

 bones, which in all probability did not belong to the same specimen, though 

 they may have belonged to the same species of the genus. The vertebrae 

 were compared with those of the Cricotus, or rather with the intercentra of 

 Cricotus, as Cope was not entirely sure at the time of the amphibian nature 

 of Cricotus. The original description of the vertebras given by Cope to 

 characterize the genus Clepsydrops is as follows : " They are deeply bicon- 

 cave, the articular cavities being funnel-shaped and continuous, thus per- 

 forating the entire length of the centrum. In a dorsal vertebra the cavities 

 communicate by a very small orifice, while in the posterior the median con- 

 traction of the canal is less marked. The posterior cavity is more gradually 

 contracted than the anterior ; in the latter the excavation is, in most of the 

 vertebrae, but slight (except beneath the floor of the neural arch), until it falls 

 rather abruptly into the axial perforation. In an (?) anterior dorsal it is as 

 widely excavated at the border as the posterior funnel. Another peculiarity 

 s the abscence of the processes of the centrum ; and a small capitular articu- 

 lation is seen sessile on the border of the cup of two of the dorsals. 



" The axis has a singular form, owing to the tubular perforation which 

 continues the posterior excavation to the anterior face of the centrum. There 

 are three articular faces, a larger subround inferior and two smaller superior, 

 which border the neural canal in front and below and are separated from 

 each other and the inferior face by the perforation in question. The anterior 

 face slopes obliquely backwards and downwards, -=nd is convex in transverse 

 section. There is no facet for the free hypapophysis of the odontoid, but it 

 appears that the inferior articular face was applied exclusively to the cen- 

 trum of the atlas, as in Sphenodon. But the axis differs from that of the 



