BETWEEN TYPICAL EEPTtLES AND OTHEB ANIMALS. 173 



both types similarly forms the back of the orbit ; but in Che- 

 louiaus it does not similarly exclude the maxillary bone from 

 entering into the orbital circle, seemingly owing to the large size 

 and forward position of the eyes. And for this reason, though the 

 nostril is single as in Crocodile, it is surrounded by the premaxillary, 

 maxillary, and prefronto-nasal bones. The upper surface of the 

 Chelonian skull is very unlike that of the Crocodile, owing to the 

 serpent-like and Chameleonoid prolongation backward of the pa- 

 rietal and supraoccipital bones, the enormous temporal fossse, the 

 double parietal and frontal bones, the general absence of distinct 

 prefrontal and lachrymal bones, and the vertical Lacertian posi- 

 tion of the maxillary. The palate is similarly closed in the me- 

 dian line ; but the nostrils are not carried back in a tube, the Testu- 

 dine arrangement in this respect reminding us as much of Chame- 

 leon as of Crocodile. And the palatal resemblance is not so close 

 as it seems at first sight to be, since, from the presence of a 

 transverse bone and downward prolongation of the pterygoid 

 bone to meet it, the lateral palatal vacuity of the Crocodile is of a 

 different nature from that of the Tortoise. In the vertebral column 

 there is scarcely any thing in common. In the tail only of Emy- 

 saura {GJielydra serpentina) there is a superficial resemblance to 

 Crocodiles, the centrum being elongated and compressed, having 

 transverse processes, a vertical articulation, and chevron bones ; 

 but the articulation is opisthocoelous, and the neural spine is sup- 

 pressed. 



The scapula and coracoid in both groups are the only bones 

 in the pectoral arch. But the Chelonian scapula is a cylindrical 

 rod ; and though in the Emydian and Testudine families the 

 coracoids have a sub-Crocodilian expansion of their distal ends, 

 they do not articulate with the sternum as in Crocodiles, or even 

 with each other. 



The Chelonian humerus is the stronger. Its radial process is 

 like that of the Crocodile, but is prolonged nearer to the hemi- 

 spherical articular head ; while on the other side a strong ulnar 

 process is prolonged beyond the articulation, and to this the Cro- 

 codile has nothing analogous. 



The compressed ulna of clawed Chelonians is unlike the bone 

 in Crocodiles. The radius is better comparable ; but in Che- 

 lonians it never has so cylindrical a shaft, and" the distal end 

 has a more simple articular surface. 



The carpal bones are not comparable. The metacarpals and 



