26 



CHELONIA. 



below the level of the head, and approximately in the same plane 

 as the ulnar process. An obturator foramen in old specimens. 



Fig. 6. 



&4 



d<-di 



Dorsal aspect of the left humerus of (A) Chelone mydas aud of (B) Lytoloma 

 crassicostatum. a, entoeondyle ; b, ectocondyle ; d, ectepi condyle ; e, ectepi- 

 condylar groove ; g, head ; h, radial (lateral) process ; i, ulnar (mesial) 

 process. (After Dollo.) 



Limbs modified into paddles, in which the phalangeals may be 

 devoid of condyles, and the terminal claws reduced to one or two. 

 Supramarginal shields are present, and there may be an intergular. 

 In the cordiform carapace of many forms the Chelonidce agree 

 with the Acichelyidce, and some members of both families differ from 

 all other Chelonia in that the anterior and posterior lateral surfaces 

 of the neurals are subequal ; from which it may be argued that 



