248 THE HORSE AND ITS RELATIVES 



E. stejionis from certain Pliocene formations in the 

 Auvergne and Velay present certain features now 

 found only among zebras. I have also shown that 

 other teeth, from a higher horizon in the Pliocene, 

 differ from the former by their larger size, the more 

 complicated folding of the enamel, the greater 

 length of the anterior pillar, and certain other 

 features connecting them with the Pleistocene 

 representatives of E. caballus, more especially those 

 molars with very complicated enamel-foldings, 

 like those from England described by Owen 

 as E. plicidcns, and those from certain French 

 caverns, such as Cindr^ and Bruniquel. 



"It appears, then, that the stenonis type was 

 extremely variable during the Pliocene, being 

 represented by forms already showing tendencies 

 towards various modern groups of EquidcB. Among 

 these forms, all of which are remarkable on account 

 of the shortness of the anterior pillar of the upper 

 cheek-teeth, some were of small size, and apparently 

 related to the asses, having the enamel-folds of the 

 cheek-teeth relatively simple, and their external 

 lobes dilated ; these seem to have developed directly 

 into the zebras of modern Africa. Others, of larger 

 size, with the enamel of the molars more plicated, 

 and the external lobes forming more pronounced 

 crescents, appear to have passed insensibly into 

 some of the larger forms of Equus caballus found 

 in certain Pleistocene formations." 



