11 



As a summary of the preceding, I propose to refer the genus 

 Champsosaurus to the order Rhynchocephalia, provisionally. It 

 differs very much from the typical genus of that order, Sphenodon, 

 in the non-coossification of the sacral vertebra?, and non-union of 

 the neural arches of the vertebra? with their centra, and the absence 

 of the chordal perforation of the latter. It differs from the ex- 

 tinct genera Glepsydrops and Gricotus, Cope, in the last men- 

 tioned two characters. On these grounds it may constitute a dis- 

 tinct suborder, under the name of Choristodera. 



It is possible that the tooth, which I referred to a new genus 

 and species, under the name of Paronychodon lacustris (Proceedings 

 Academy, 1876, October), may belong to one of those of the pre- 

 sent genus. In that case the older generic name takes precedence 

 of the later. I may add that some vertebrae of this genus have 

 been figured and described by Dr. Leidy in the Transactions of 

 the American Philos. Society, 1860, without name. 



I recognize four species among the vertebra?, chiefly by charac- 

 ters observed in the cervical region. There is a great discrepancy 

 of size among them, and the small ones may be immature. 

 Champsosaurus profundus, sp. nov. 



This species is chiefly known from a series of vertebra? found 

 together, and having every appearance of pertaining to the same 

 animal. It consists of a cervical, three dorsal, and a sacral ver- 

 tebra?. Other isolated vertebra? of several individuals present 

 similar characters. 



The primary feature is the great vertical diameter of the dorsal 

 vertebra? as compared with the transverse measurement. This is 

 occasioned by the great development of the inferior keel, to which 

 the sides of the centrum converge, without concavity. In corre- 

 sponding centra of the G. annectens the inferior face is merely 

 angulate. Another character is the obliquity of the articular 

 faces to a vertical plane drawn at right angles to the long axis of 

 the centrum. This is most strongly marked on posterior dorsals, 

 where the inferior keel is less prominent. The sacral vertebra has 

 a depressed form. 



An anterior caudal vertebra may belong to this or an undescribed 

 species. It has rudiments only of the chevron-facets, and having 

 a large neural arch, is doubtless from the anterior part of the 

 series. It is more compressed than the corresponding one in G. 



