THE FORERUNNERS OF THE HORSE 247 



members of the genus ; the primitive feature being 

 the shortness of the antero-internal pillar of those 

 of the upper jaw. There is also a slight depression 

 in the wall of the skull immediately in advance 

 of the socket of the eye. Nearly allied to Steno's 

 horse is Equus sivalensis, of the Pliocene deposits 

 of the Indian Siwaliks, which, as already mentioned, 

 exhibits both the aforesaid features. So far as can 

 be determined, this Siwalik horse seems to have 

 stood about 15 hands at the shoulder, and to have 

 had a relatively big head, and slender cannon-bones, 

 with proportionately large splints. 



After mentioning that in respect of their upper 

 molars Equtis stenonis and E. sivalensis occupy an 

 intermediate position between the modern members 

 of the genus and the extinct Pliocene Protohippus, 

 Prof. Marcellin Boule^ proceeds to observe that 

 when a large series of the remains of the first-named 

 species is studied, " it will be found that in respect 

 of stature, of the plications of the enamel of the 

 upper molars, and of the shape of their inner pillars, 

 Equus stenonis presents individual variations com- 

 parable to those which occur in the different 

 varieties or races of the horse, both of the Pleisto- 

 cene and modern epochs. Certain teeth, of relatively 

 small size, display remarkable resemblances to those 

 of the ass ; and I have shown that milk-teeth of 



^ "Les Chevaux fossiles des Grottes de Grimaldi," Ann. de PaUon- 

 tologie, vol. V. p. 130, 1 9 10, 



