94 Vertebrata. 



and the hardest layer of the teeth (the enamel), is 

 arranged in crescents; these are known as Ruminants. 

 FIG Of the btmodonts the pigs are the 



most familiar examples. Our domes- 

 tic pigs are derived from the wild 

 boars of Southern Europe and Asia, 

 animals which formerly inhabited 

 Great Britain in a wild state. The 

 babyroussa of the Malay Islands is 

 Crown of the tooth of a singular pig whose upper canine 

 Lf m e e r ic s resfs. the teeth grow upwards and arch back- 

 wards so as to reach the forehead 

 where they end in a curled point. Most of the pigs 

 have large tusk-like canines, and their teeth are usually 

 represented by the formula 



33 i -i 33 33 



The hippopotamus of the rivers of Africa is an 

 enormous pig-like creature, with very short legs and 

 a heavy body, and with long tusk-like incisors, two in 

 each jaw ; it sometimes reaches a length of nine feet. 

 60. Ruminants. The ruminants are so called 

 because they chew the cud, that is, they subject their 

 food to a second chewing after it has been swallowed. 

 They are, for the most part, large soft-fleshed animals, 

 the favourite prey of large carnivores, and as the food 

 which they require for their nourishment is bulky, 

 being green herbage, and only to be obtained in open 

 places of pasturage, where they would be exposed 

 without shelter to the assaults of their enemies, it 

 becomes a matter of vital importance for their well- 



