BETWEEir TYPICAL REPTILES AND OTHER ANIMALS. 181 



The fibula of the bird is unlike the Chelonian's in having no 

 distal end ; but the proximal end similarly articulates with a facet 

 on the outside of the femur. The tibia of the bird would only 

 approximate to that of the Chelonian before its proximal and 

 distal epiphyses were anchylosed. As it is, there is no close re- 

 semblance ; and no resemblance at all is found in the tarsus, 

 metatarsus, and phalanges. 



§ 3. The Grocodilian Characters of Chelonians. 

 [See also the Chelonian characters of Crocodiles, p. 172.] 



These characters, properly so called, may in the cranium be 

 regarded as the growing together of the squamosal, parietal, and 

 postfrontal bones, which in the Crocodilia leave only a small 

 temporal fossa between them, while in the marine Chelonia the 

 growth has extended till the foramen is obliterated. Similarly 

 there may be supposed in Crocodiles a tendency of the squamosal 

 and postfrontal bones to grow down to meet the quadrate -jugal 

 and malar, which growth is seen perfected in Chelone, though the 

 quadrato-jugal bone is vertical. On the other hand, by enlar- 

 ging the temporal fossa in the Crocodile so as to divide the post- 

 frontal from the squamosal bone (towards which there may be 

 supposed a tendency in Crocodiles with the temporal fossa largest, 

 such as the great Gravial), the postorbital features of the Croco- 

 dilian head would approximate towards the Testudinata. In the 

 vertebral column there "is no character which can be considered 

 to be Crocodilian, the long tail and chevron bones of Emysaura 

 being associated with an opisthocoelous centrum, which hitherto 

 has not been found in a Crocodile : though occurring in the tail 

 and neck, it may be considered eminently Chelonian, and is pro- 

 bably only obscured in the back by the formation of the cara- 

 pace. 



"What the pectoral arch would have been but for the peculiar 

 envelope of the Chelonian it is difficult to judge ; but as it 

 stands, no Crocodilian characters can be recognized. The only 

 Crocodilian feature of the humerus is the radial crest, which it 

 shares with birds, the Chameleon, and a few mammals. 



The elongation of the proximal carpal bones under the ulna in 

 Chelone is paralleled in Crocodiles. And tlie elongation of the 

 metacarpals and plialanges of Crocodiles is better matched in the 

 marine than the land Chelonia. 



13* 



