184 



FOSSIL TURTLES OF NORTH AMERICA. 



The lower jaw (fig. 237) is nearly complete. The crushing-surface has a width of 18 mm. 

 and is convex transversely. The cutting-edge is acute and directed outward, possibly due 

 partly to distortion. The tip of the jaw appears to have been somewhat upturned as a beak, 

 and there is a corresponding pit in the upper jaw just behind the premaxillae. The symphysis 

 has a length of 35 mm. 



The humerus is crusht very flat and the ulnar process is broken off. The length of the bone, 

 measured from the proximal surface of the head to the distal end, is 156 mm. The impression 



FIGS. 236 AND 23J.-Porthochelys browni. 

 Skull and lower jaw of type. Xi- 



236. Palatal surface, m.v, maxilla; fa!, palatine; 



pi, ptcrygoid; qu, quadrate; vom, vomer. 



237. Lower jaw. ting, angular; art, articular; 



dart, dermarticular; den, dentary; sur, 

 supraangular. 



of nearly the whole head appears on the upper side of the flattened bone; hence it is evident 

 that the head was directed upward when the bone was horizontal and not as it is in the 

 Cheloniidae. The radial process was connected with the head and there existed a broad exca- 

 vation, or fossa, between this process and the ulnar process. In short, the humerus appears 

 to have had practically the form of that of Chelydra. 



The distal end of the femur is missing, but the bone was at least nearly as long as the 

 humerus. It was, however, a slenderer bone. 



The ilium resembles closely that of Toxochelys. 



Family DESMATOCHELYID^E Williston. 



Skull with temporal region rooft over as far backward as the occipital condyle. Large 

 nasal bones present. Choanae placed well forward, not underfloored by the vomer, maxillae, 

 and palatines. Small posterior palatine foramina present. Humerus indicating a paddle-like 

 fore limb. Plastron loosely joined to the carapace. 



The type of this family is the genus Desmatochelys, but the genera Atlantochelys and 

 Neptunochelys are provisionally included. The two latter are known only from humeri. 

 These are not greatly different from the same bones in the Cheloniidae. 



Genus DESMATOCHELYS Williston. 



Desmatochelys, WILLISTON, Kansas Univ. Quart., Ill, 1894, p. 5. 

 Desmochelys, BoULENGER, Zool. Record, Reptiles, 1895, p. 29. 



The generic characters are not yet to be distinguish! from those of the family. 

 The type of the genus is Desmatochelys lowi Williston. 



