22O ANIMAL BIOLOGY 



ally hibernate in caves, hollow trees or other dark places 

 to which they commonly retreat during the day. 



The order Ungulata, the hoofed animals, constitutes 

 one of the largest and most important groups of mammals. 

 In general ungulates are herbivorous; their molar teeth 

 are fitted for grinding and the canines are usually small 

 or wanting. The order is commonly divided into the 



FIG. 172. African elephant. (After Baker.) 



odd- toed ungulates (Perissodactyla), such as the horse, 

 tapir and rhinoceros; the even-toed ungulates (Artio- 

 dactyla), such as the ox, sheep, deer, camel, pig, hippo- 

 potamus; and the Proboscidea, or elephants. 



Some of the even-toed ungulates such as the deer, 

 sheep and oxen are called ruminants on account of their 

 habit of chewing a cud. Most of these animals have a 

 four-chambered stomach, one division of which receives 



