NATURAL SCIENCES OF PHILADELPHIA. 233 



White River tertiary formations, and with associated remains of ITijopota- 

 mus and Titanotherium, probably indicates the end of the eocene, which was 

 succeeded by the more extensive raiocene deposits of the Mauvaises Terres, and 

 the pliocene deposits of the Niobrara River. 



On some Cretaceous BEFTILIA. 

 BY E. D. COPE. 



NATANTIA. 



CLIDASTES Cope. 



This genus is established on a species represented by a single dorsal verte- 

 bra, which was found by my friend Prof. 0. C. Marsh, of Yale College, in a 

 marl pit near Swedesboro', Gloucester Co., N. J. Its form is highly character- 

 istic, and resembles considerably that of such genera of Iguanidte as Euphryne 

 and Dipsosaurus, and in some degree those of Cyclura and Iguana. It differs 

 from the dorsals of known serpents in having a zygosphen on the plane of 

 the anterior zygapophysis, and in having the costal articular surface continu- 

 ous with and covering the diapophyses. It differs from the genera of Iguanida* 

 mentioned in the very small amount of upward direction which the face of the 

 articular ball of the centrum exhibits. This face is nearly vertical, meeting 

 the lower plane at a slightly less angle than the upper. It is much more 

 strongh^ convex transversely than vertically. The neural arch rises from the 

 anterior three-fourths of the centrum, the zygapophysis coming off from the 

 edge of the cup, and the diapophysis fi'om -2 of the length behind it. The 

 zygapophysis is more prominent than the zygosphen, and the sinus between 

 them is floored by a thin horizontal plate at its fundus. 



The general form of the vertebra is depressed. The zygapopliyses are 

 spread apart, and their outer margin continues in a straight line from the dia- 

 pophyses. The diapophyses are directed upwards, and are vertical compressed 

 in form ; they are opposite to about equal portions of the centrum and neural 

 arch. Their posterior face is slightly concave, and the upper face behind forms, 

 with the neural arch, a deeply concave line. The convexity of the ball is not 

 so great as in the Crocodilia, and, with the thin lipped cup, resembles that of 

 Mosasaurus ; this resemblance is heightened by the slightly depressed upper 

 outline of the ball, and the form of the diapophyses. The inferior face of the 

 centrum presents a median obtuse ridge, and nearly flat lateral faces, which 

 are concave antero-posteriorly. The cup is broader than deep, and has a 

 slightly concave outline ; the base of the zygosphen originates opposite the 

 middle of the neural canal. The latter is a broad vertical oval. 



ClilDASTES IGUANAVUS CopC, Sp. UOV. 



In this species the articular face of the zygosphen is inclined at an angle of 

 45°, while that of the zygapophysi^'is a little more horizontal. The posterior 

 zygapophyses are broken oS". 



In. Lin. 



Length of centrum below , 2 O-o 



Width of cup 1 6-8 



Depth " 1 1-5 



Width between extremities diapophysis 3 0-5 



Depth articular face diapophyses. lO-o 



From diapophysis to end zygapophysis & 



Between zygosphen and zygapophysis 4-5 



Width centrum anterior to ball 15 



Width of neural canal behind 5-5 



While there is a probability that this animal was a forerunner of the Igua- 

 nian type of Lacertilia, it possessed, no doubt, strong relationships to Mosasau<- 



1868.] 16 



