UNGULATA. 585 



broad hoof, without supplementary hoofs (fig. 249, A).* There 

 is a discontinuous series of teeth in each jaw ; and in the 

 males, canines are present, but these are wanting in the females. 

 The dental formula is 



Q 



33 i i 33 33 



The skin is covered with hair, and the neck is furnished with 

 a mane. 



The family Equidce is divided by Dr Gray into two sections 

 or genera : Equus, comprising the Horse ; and Asinus, com- 

 prising the Asses and . Zebras. Many authorities, however, 

 place all the existing forms under the single genus Equus. 



The genus Equus is distinguished by the fact that the animal 

 is not banded, and has no dorsal line ; both the fore and hind 

 legs have warts, and the tail is hairy throughout. The genus 

 appears to contain no more than one well-marked species, as 

 far as living forms are concerned namely, the Equus caballus. 

 From this single species appear to have descended all the 

 innumerable varieties of horses which are employed by man. 

 The native country of the horse appears to have been Central 

 Asia, but all the known wild individuals of the present day 

 appear to be descendants of domestic breeds. 



The genus Asinus is characterised by the fact that there is 

 always a distinct dorsal line, and the body is more or less 

 banded ; the fore-legs alone have warts, and the tail has a tuft 

 of long hairs at its extremity. The Ass is probably a native 

 of Asia (where the wild Ass is at present a native), and there 

 appears to be little doubt but that the common Ass is merely 

 the domesticated form of the wild Ass (Equus onager). An- 

 other well-known species is the mule-like " Djiggetai" (Asinus 

 hemionus) of Central Asia. The striped members of this sec- 

 tion are known as Zebras and Quaggas, and are natives of the 

 southern parts of Africa. 



SECTION B. ARTIODACTYLA. In this section of the Ungu- 

 lates the number of the toes is even either two or four and 

 the third toe in each foot forms a symmetrical pair with the 

 fourth (fig. 249, B, C). The dorso-lumbar vertebrae are nine- 

 teen in number, and there is no third trochanter on the femur. 

 If true horns are present, these are always in pairs, and are 

 supported by bony horn-cores. The antlers of the Deer are 

 also paired, but they are not to be regarded as true horns. 

 The stomach is always more or less complex, or is divided into 



* In the extinct Hipparion there are two rudimentary lateral toes ; and 

 in the still more ancient Anchitherium these toes touch the ground. 



