chap, xvn.] 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 Babirusa) ; and, 

 3. ThePhacochcerinpe, 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 Red 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. 



Sus (14 species), ranges over the Palasarctic 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. Potamochoerus (3 species ?), is wholly Ethiopian 

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

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



Phacochoerus (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 SuidoB. — 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, Botliriodon, Anthracothcrium, Palceochcerus, Hyotherium, 

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

 Chwropotamus, 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, Elothcrium, Per- 

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

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

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



Vol. II.— 15 



