VERTEBRATA : MAMMALIA. 705 



continent. It is an enormously bulky and unwieldy animal, 

 reaching a length of eleven or twelve feet. It is nocturnal in 

 its habits, living upon grass, the foliage of trees, and herbs, 

 and it swims and dives with great facility. It is found in 

 tolerable abundance in the rivers of Abyssinia, and occurs 

 plentifully in South Africa. A much smaller form (the so- 

 called Hippopotamus or Chceropsis Liberiensis] occurs on the 

 west coast of Africa, but it is exceedingly rare, and compara- 

 tively little is known about it. It possesses, however, only 

 two lower incisors instead of four. 



Fam. 2. Sitida. The group of the Suida, comprising the 

 Pigs, Hogs, and Peccaries, is very closely allied to the pre- 

 ceding ; but the feet (fig. 388) have only two functional toes, 

 the other two toes being much shorter, and hardly touching 

 the ground. All the three kinds of teeth are present, but they 

 vary a good deal. The canines (fig. 402) always are very 



Fig. 402. Skull of the Wild Boar (Sns scrofaferus). (After Gray.) 



large, and trihedral in shape; and in the males they usually 

 constitute formidable tusks projecting from the sides of the 

 mouth. The incisors are variable, but the lower ones are 

 always inclined forwards. The molars and prasmolars have 

 broad crowns, with two transverse ridges (increased to three 

 or more in the last molar), which are divided into rounded 

 tubercles (fig. 398). The permanent dental formula of the 

 Boar (Sus scrofa) is 



i 3-3 ; c in! ; p m 3-3 . m 3-3 = . 



33 i i 33. 33 



In the young animal there are four deciduous molars, but the 

 first of these is not replaced by a pnemolar, though it remains 



2 Y 



