HORSES. 



9 



"mark." In the skull the enclosure of the socket of the eye by 

 a complete bony ring is also unknown in the other members of the 

 suborder. In all existing Horses there is only one toe on each 

 foot, although rudiments of lateral digits are represented by the 

 te splint-bones" on each side of the upper end of the cannon-bones. 

 In the extinct three-toed Horses (Hipparioyi) there were three 

 complete digits to each foot, although the lateral pair was small. 

 In the earlier Arte hit her ium the lateral toes were relatively larger, 

 and the molar teeth had short crowns, with the valleys free from 

 cement. From this animal there is a transition to the small four- 

 toed Hyracotherium, which was not larger than a fox, and formed 

 one of the earliest ancestors of the family. A series of specimens 

 illustrating the ancestry of the Horse, and another displaying the 

 alterations in the teeth with age are shown in the North Hall. 

 Horses, Zebras and Asses are inhabitants of open plains, where 

 they wander in droves headed by an old stallion. 



The Horse [Equus caballus) is markedly distinguished 

 Horse ^ rom ^ De °t Qer species of the genus by having the tail 

 completely clothed with long hairs, and by the long flowing 

 mane. It has bare callosities on both pairs of limbs, instead of on 

 the front pair alone ; and the head is relatively smaller, the ears are 

 shorter, the limbs longer, and the hoofs broader. 



Two distinct types of Horse, in many instances largely modified 

 by inter-breeding, appear to exist. 



1st. — The Northern, or Dun type, represented by the Dun 

 Ponies of Norway [Equus caballus typicus), the closely allied 

 Celtic Pony (E. c. celticus). of Iceland, the Hebrides, etc., and 

 the Wild Pony of Mongolia [E. c. prezewalskii) , to which the 

 now extinct Tarpan of the Russian steppes appears to have come 

 very close. The prevalent colour is yellow-dun, with dark brown or 

 black mane, tail, and legs ; in the wild breed the muzzle is often 

 white and the root of the tail short-haired ; while the head is 

 relatively large and heavy. No depression exists in the skull in 

 front of the eye. Most of the ordinary Horses of N.W. Europe 

 are descended from the dun type, with more or less admixture of 

 Barb blood. 



2nd. — The Southern, or Barb type, represented by Barbs, Arabs, 

 Thoroughbreds, etc. (E. c. asiaticus, or libycus), in which the 



