246 THE HORSE AND ITS RELATIVES 



As mentioned in earlier chapters, the Prehistoric 

 and Pleistocene deposits of Europe and Turkestan 

 have yielded remains inseparable for the most part 

 at any rate from the modern horse {Equus caballus]^ 

 of which they probably represent several phases 

 or races, while others have been assigned to the 

 ass (E. asinus\ and yet others to the onager 

 (E. onager). From the Pleistocene gravels of the 

 Narbada Valley, in Central India, have been 

 obtained skulls and other remains of a horse (E. 

 namadicus) characterised by the elongation of the 

 grinding surface of the anterior pillars on the inner 

 side of the upper cheek-teeth ; the same species 

 also occurring in the topmost beds of the Siwaliks 

 of Northern India. 



In North America the Pleistocene and Upper 

 Pliocene formations have yielded remains of at 

 least nine extinct members of the modern genus ; 

 one of these, E. fraternus, closely resembling E. 

 caballus, while a second, E. giganteus, from South- 

 western Texas, appears to have been the largest of 

 the whole group ; the cheek-teeth exceeding those 

 of the biggest cart-horses by more than one-third 

 the diameter of the latter. 



In the Upper Pliocene deposits of the Val 

 d'Arno and other parts of Europe, including the 

 so-called Forest Bed of the coast of Norfolk, occurs 

 a horse (E. stenonis) with molars of a somewhat 

 more primitive . type than those of the existing 



