CHAP. XV] I.] MAMMALIA. 215 



peccaries (1 genus, Dicotyles). These offer so many structural 

 differences that they are often classed as a separate family. 2. 

 The true swine (3 genera, Sus, Potamochoerus, and Babirusd) ; and, 

 3. ThePhacochcerinte, or wart hogs (1 genus, Phacochcerus). These 

 last are also sometimes made into a separate family, but they 

 are hardly so distinct as the Dicotylinse. 



The Peccaries (2 species), are peculiar to the Neotropical re- 

 gion, extending from Mexico to Paraguay. They also spread 

 northwards into Texas, and as far as the Eed Eiver of Arkansas, 

 thus just entering the Nearctic region ; but with this exception 

 swine are wholly absent from this region, forming an excellent 

 feature by which to differentiate it from the Palsearctic. 



)$us (14 species), ranges over the Palsearctic and Oriental regions 

 and into the first Australian sub-region as far as New Guinea ; 

 but it is absent from the Ethiopian region, or barely enters it on 

 the north-east. Potamochcerus (3 species ?), is wholly Ethiopian 

 (Plate V. vol. i. p. 278). Bahirusa (1 species), is confined to two 

 islands, Celebes and Bouru, in the first Australian sub-region. 



Phacochcerus (2 species), ranges over tropical Africa from 

 Abyssinia to Caffraria. 



Dr. J. E. Gray divides true swine {Sus) into 7 genera, but it 

 seems far better to keep them as one. 



Fossil Suidce. — These are very numerous. Many extinct 

 species of wild hog (Sus), are found in Europe and North India, 

 ranging back from the Post-pliocene to the Upper Miocene for- 

 mations. In the Miocene of Europe are numerous extinct 

 genera, Bothriodon, Anthracotherium, Palccochcerus, Hyotherium, 

 and some others ; while in the Upper Eocene occur GebocluErus, 

 Cheer opotamus, and Acotherium, — these early forms having more 

 resemblance to the peccaries. 



None of these genera are found in America, where we have the 

 living genus Dicotyles in the Post-pliocene and Pliocene deposits, 

 both of North and South America ; with a number of extinct 

 genera in the Miocene. The chief of these are, Elotherium, Pcr- 

 chcerus, Leptochcerus, and Nanohyus, all from Dakota, and 

 Thinohyus, from Oregon. One extinct genus, Platygonus, closely 

 allied to Dicotyles, is found in the Post-pliocene of Nebraska. 



Vol. II.— 15 



