43O ORDERS OF MAMMALIA. 



In the Tertiary deposits of the Siwalik Hills in India (Mio- 

 cene) have been discovered several species of Hippopotamus, 

 belonging to the sub-generic type, Hexaprotodon. 



2. Suida. The group of the Suida, comprising the Pigs, 

 Hogs, and Peccaries, is very closely allied to the preceding ; 

 but the feet 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 always are very large, and in the males they usu- 

 ally constitute formidable tusks projecting from the sides of 

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

 always inclined forwards. The molars vary from three to 



seven on each side of the mouth (^ * or Z '-}. The stom- 



33 77 



ach is mostly slightly divided, and is not nearly so complex as 

 in the Ruminants. The snout is truncated and cylindrical, 

 fitted for turning up the ground, and is capable of consider- 

 able movement. The skin is more or less abundantly covered 

 with hair, and the tail is very short, or represented only by a 

 tubercle. 



The most important genera of the Suida are Sus (Pigs), 

 Dicotyles (Peccaries), Charopotamus, Hyopotamus, and Anthra- 

 cotherium, of which the three last are extinct. 



The genus Sus, comprising the true Pigs, appears to have 

 commenced its existence in the Miocene Tertiary. Several 

 species are known from Pliocene deposits ; and the Wild 

 Boar (Sus scrofa) has been found in Post-Pliocene accumula- 

 tions (commencing in the prae-glacial forest-bed of Norfolk). 



The genus Dicotyles, comprising the existing Peccaries, is 

 at present confined to the American continent. The same 

 country also has yielded five fossil species, which have been 

 found in the bone-caves of Brazil, and two of which appear to 

 have been much larger than the living forms. 



Chceropotamus comprises some Upper Eocene Suida, which 

 possess seven molars on each side of each jaw, the first of 

 these (prsemolars) being compressed, whilst the others are 

 tuberculate. The canines are short, and are not exserted, as 

 they are in the Wild Boar. Hyopotamus is another genus, in 

 which the canines are short. All the species of this latter 

 genus belong to the Upper Eocene and Lower Miocene Ter- 

 tiary. Lastly, the genus Anthracotherium is nearly allied to 

 Chczropotamus, with which it agrees in the number and general 

 form of the praemolar and molar teeth. All the known species 

 of this genus belong to the Lower Miocene. 



3. Anoplotheridcz. Forming a kind of transition between 



