1 1 6 Bulletin American Museum of Natural History. [Vol. XIII. 



the anterior premolar to the top of the nasals is much greater in 

 E. scotti. The processes of the frontals inclosing the posterior 

 portion of the orbits, slope more backward and are much nar- 

 rower than in E. caballus. The occiput seems to be more over- 

 hanging ; this is due probably to the great shortening 'of the 

 basioccipital bone. The basioccipital ridge is not so compressed 

 and the fossae inclosed between the paroccipital processes and the 

 condyles are much deeper. In these last two characters E. scotti 

 (Fig. 5, A) is like E. occidentalis Cope (not of Leidy).' The pos- 

 terior region of the skull, the posterior nares and the palate are 

 narrower than in E. caballus. 



Fig. 5. A^ occipital view of E. scotti \ B, occipital view of E. caballus. 



The lower jaw is more massive especially in the dental region. 

 The jaw is much deeper, to accommodate the very long crowns 

 of the molar-premolar series. This, together with the increased 

 vertical thickness of the anterior portion of the skull, gives the 

 whole head a more massive and less graceful form than that of 

 E. caballus. Owing to the greater antero-posterior length of the 

 molar-premolar series, the jaw seems to curve upward much more 

 abruptly from the posterior molar. The symphysis mandibuli is 

 heavier and longer than in E. caballus., extending back of the 

 mental foramina. The jaw seems compressed laterally at the 

 posterior part of the symphysis, owing to the wide expansion, 

 anteriorly, to accommodate the wide incisors. 



The other bones of the skeleton, taken separately, seem to be 

 indistinguishable from those of E. caballus. 



Proc. Am. Phil. Soc, Vol. XXII, p. 11. 



