ORDERS OF MAMMALIA. 323 
expanded nail or “oof. There are never more than four full- 
sized toes to each leg, and owing to the presence of hoofs the 
limbs are useless for grasping, and are only of use in locomo- 
tion and in supporting the weight of the body. There are 
always two sets of teeth, and the molars have broad crowns 
adapted for grinding vegetable substances, 
The Ungulata are divided into two great primary sections, 
according as the toes are even or odd in number :— 
A. Perissodactyla, or Odd-toed Ungulates, in which the toes 
are odd in number—etther one or three.* If horns are 
present, they are not in pairs. 
4. Artiodactyla, or Even-toed Ungulates, in which the toes 
are even in number—etther two or four; and if horns are 
present, they are in pairs. 
The living Perissodactyle Ungulates are the Riinaeews, the 
Tapirs, and the Horse and its allies. The RAznoceroses are ex- 
tremely large and buiky brutes, having a very thick and nearly 
Fig. 175.—Ungulata. A, Perissodactyle foot of Zebra; B, Artiodactyle foot of 
Llama ; C, Artiodactyle foot of Antelope ; D, Perissodactyle foot of Rhinoceros. 
hairless skin, usually thrown into deep folds. The feet (fig. 175, D) 
are furnished with ¢kree toes each, all encased in hoofs. The 
nose is furnished with one or two horns, composed of longitud- 
inal fibres compacted together, and not having any central core 
of bone. When there is only one horn, it is, of course, unsym- 
metrical; and when there are two, these are not paired, but 
* The fore-feet of the Tapirs are even-toed, but the hind-feet are perissodactyle, 
