1881.] xvo [Cope, 



Champsosaukus ptjekcensis, sp. nov. 



I have already announced the discovery * of this Laramie genus in the 

 Puerco beds of New Mexico, and described a species, G. australis, from 

 that region. I now introduce two additional species from the same hori- 

 zon. One of these is represented by a number of fragments which include 

 three dorsal and four caudal vertebrae of apparently one individual. They 

 represent an animal of larger size than any of those heretofore referred to 

 Ghampsosaurus, excepting the G. vaceinsulensis. In all of the vertebra? 

 the neural arch is more or less coossified with the centrum, and the animal 

 had probably reached its full size. 



One of the dorsal centra is split vertically and longitudinally, and shows 

 the structure already figured by Leidy in the Iscliyrosaurus antiquusf 

 Leidy. The'surface exposed displays two diagonal lines of fissure cross- 

 ing each other at right angles. They indicate clearly the mode of origin 

 of this amphiplatyan type of centrum. The centrum is first deeply am- 

 phiccelous as in the Theromorphous reptiles of the Permian. The conical 

 cavities are filled by the ossification of the remaining portions of the noto- 

 chord, forming a conical body which always remains distinct from the re- 

 mainder of the centrum. 



The articular faces of the dorsal centra are a little wider than deep, and 

 the depth about equals the length of the body. They are not nearly so 

 depressed as those of G. australis, and their outline is different. This is 

 Avider above and narrows below ; in both G. australis and G. saponensis the 

 inferior outline is part of a circle. None of the dorsals preserved are 

 keeled below. There is a fossa below the diapophysis which has a subver- 

 tical posterior boundary. The general surface (somewhat worn) does not 

 display wrinkles near the articular faces. An anterior dorsal has a short 

 compressed diapophysis with a narrow figure 8 articular surface, and its 

 superior border is in line with the roof of the neural canal. The anterior 

 caudals have subround articular faces ; the posterior are more oval and 

 the bodies compressed. With greater compression, the length increases. 



Measurements. M. 



r anteroposterior 025 



Diameters of an anterior dorsal 1 vertical 025 



' transverse 030 



Height of costal facet of do 021 



-p.. , , ii^ vertical 007 



Diameters neural canal do. ] 



t transverse 009 



/ anteroposterior 024 



Diameters anterior caudal < vertical 021 



' transverse 021 



/anteroposterior 025 



Diameters posterior caudals < vertical 018 



' transverse 018 



* American Naturalist, 1881. p. 669. 

 t Transac. Anier. Philos. Soc. 1860. 



