OSTEOLOGY OF AMERICAN PERMIAN VERTEBRATES 401 



small, and may have been absent; the hand upon the whole seems 

 to have been much like that of Varanosaurus hrevirostris . The 

 lengths of the anterior ribs are determined from one specimen in 

 which they are preserved nearly completely in relation with the 

 vertebrae. The lengths of the posterior ribs are conjectural. It 

 is also assumed that there are not more than seven cervical verte- 

 brae; there is a strong possibility, however, that the neck was 

 longer. 



In the life restoration (Fig. 8) I have added the tail in like 

 proportion to that of slender living lizards. That it was as long 

 as the head, neck, and trunk 

 together there can be scarcely 

 a doubt, for it is not often 

 shorter in swift-crawling rep- 

 tiles; it may have been longer. 

 In much probability the living 

 animal was covered with cor- 

 neous scales; one can hardly 

 conceive of a reptile with habits 

 such as Araeoscelis must have 

 had as having a bare skin, and 

 it is quite certain that the body 

 was not protected with bony 

 scutes. 



HABITS 



Just what is the significance 

 of some of the peculiar charac- 

 ters possessed by Araeoscelis I 

 am at a loss to conjecture. 

 That the creature was a swift- 

 moving, crawling reptile there 

 can be no doubt. That it was 



arboricolous I also believe; the pointed and curved ungual pha- 

 langes determine the presence of sharp claws in the living animal. 

 The unusual development of the calcaneum and outer toes seems 

 to indicate springing habits, and the curved femora and elongated 

 epipodials resemble those of Scleromochlus, of whose leaping powers 



Fig. 7. — Araeoscelis gracilis Williston: 

 Restoration of skeleton, about one-fourth 

 natural size. 



