CHAP. XVII.] 
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, Sits, Potamochc&rus, and Babirusa ) ; and, 
3. The Phacochoerime, or wart hogs (1 genus, Plwcochcerus). These 
last are also sometimes made into a separate family, but they 
are hardly so distinct as the Dieotylinee. 
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 River of Arkansas, 
thus just entering the Neurotic region ; but with this exception 
swine are wholly absent from this region, forming an excellent 
feature by which to differentiate it from the Pahearctie. 
Sus (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 Y. vol. i. p. 278). Babirusa (1 species), is confined to two 
islands, Celebes and Bouru, in the first Australian sub-region. 
Phacochmrus (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, Anthracotheriurn, Palceochcerus, Hyotheriicm, 
and some others; while in the Upper Eocene occur Cebochcerus , 
(Jhmropotamus, 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, Elotheriwm, Per - 
choerus, 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. 
