EQUID^E 381 



of North America, there were three digits in the feet (Fig. 156, d) ; 

 but in the Indian H. antilopinum (separated by Cope as Hippo- 

 dactylus) the lateral digits seem to have disappeared. There is 

 some doubt whether or no Hipparion should occupy a place in the 

 direct ancestry of the Horse, and Professor Cope suggests that while 

 in America the intermediate place between Anchitherium and Equus 

 was held by Protohippus, in Europe the same position was occupied 

 by Hipparion a view which involves the dual origin of the Horses 

 of the New and Old Worlds. 



Equus. 1 Upper cheek-teeth with the anterior pillar (except in 

 a very early stage of wear) joined by a narrow neck to the 

 adjacent column (Fig. 157, c). Each foot with a single complete 

 digit, but with remnants of the proximal portions of the second 

 and fourth metapodials (Fig. 156, e) ; some extinct forms having 

 claw-like rudiments of the terminal phalangeals of the lateral digits. 

 First upper premolar very small or altogether absent in existing 

 species, but in some fossil species larger and persistent; first 

 lower premolar only occasionally developed in some fossil forms. 

 Ears long. Tail long, with long hairs either at the end or 

 throughout. A callosity on the inner side of the fore limb above 

 the carpus. 



Fossil Species. In the Pleistocene Horses of South America 

 described as Hippidium, as well as in the closely allied ones from 

 North America for which the name Pliohippus has been proposed, 

 the upper molars are shorter and more curved than in the existing 

 species, while their anterior pillar is not longer antero-posteriorly 

 than in Hipparion; the lateral claw-like hoofs persisting. Some of 

 the European Pliocene species (like E. stenonis) agree with these 

 species in the form of the grinding surface of the anterior pillar 

 of the upper molars. In one of the species from the Lower 

 Pliocene of India (E. sivalensis) which was a contemporary of 

 Hipparion and in all the existing species, the grinding surface of 

 the pillar in question is greatly elongated in the antero-posterior 

 direction, as in Fig. 157, c. 



Fossil remains of Horses are found abundantly in deposits of 

 the most recent geological age in almost every part in America, 

 from Eschscholtz Bay in the north to Patagonia in the south. In 

 that continent, however, they became quite extinct, and no Horses, 

 either wild or domesticated, existed there at the time of the 

 Spanish conquest, which is the more remarkable as, when intro- 

 duced from Europe, the Horses that ran wild proved by their 

 rapid multiplication in the plains of South America and Texas that 

 the climate, food, and other circumstances were highly favourable 

 for their existence. The former great abundance of Equidce in 

 America, their complete extinction, and their perfect acclimatisation 

 1 Linn. Syst. Nat. 12th ed. vol. i. p. 100 (1766). 



