114 Bulletin American Museum of Natural History. [Vol. XIII, 



T^- ,, ^ c c \ \ antero-posterior 25 mm. 



Diameters of crown of m' i ^ *^ ■' 



{ transverse 25.5 mm. 



Long diameter of i' 18 mm. 



Total length of molar-premolar series 172 mm. 



Thus it is seen that while the skulls of these individuals rep- 

 resenting two species are of about the same size, the teeth of 



Fig. 3. Skull of E. scotti, 



E. scotti (Fig. 3) are much larger and the whole masticating ap- 

 paratus is proportionately shorter and better adapted to grazing 

 than in E. caballus (Fig. 4) ; although the proportion of teeth 

 to skull is not much greater than in the pony. The teeth seem 

 to differ from E. eous Hay,' a species from Louisiana described 

 by Cope under the name of E. interniedius!^ only in tlieir some- 

 what larger size. 



' Science, 1899, p. 593. 



= Proc. Am. Phil. Soc, Vol. XXXIV, p. 463. 



