374 GEOGRAPHICAL AKD GEOLOGICAL DISTRIBUTION. 



The recent hogs are commonly divided into three more or less 

 distinct groups : the peccaries (genus Dicotyles), whose range 

 comprises the region included between Arkansas and Paraguay ; 

 the wart-hogs (Phacochoerus) of East and South-Central Africa; 

 and the true swine, under which are ranged the hog proper (Sus), 

 the babyrousa (Babirusa), and river-hog (Potamochoerus). The 

 last is exclusively West African, while the babyi'ousa is confined 

 to Celebes, and some of the smaller islands of the Eastern Archipel- 

 ago (Bouro, &c.). Much diversity of opinion still exists as to the 

 number of species that are comprised in the genus Sus. Some 

 fifteen or more have at various times been recognised by zoolo- 

 gists, but by Forsyth Major,'-" who has probably enjoyed better 

 opportunities for making a critical study of the group than any of 

 his predecessors, the number is restricted to four, with a probable 

 fifth one, concerning which we know little, but which appears to 

 occupy a considerable part of the Ethiopian region : Sus vittatus, 

 whose distributional area extends from Sardinia to New Guinea, 

 and from Japan to Damara-Land (Southwest Africa) ; S. verrucosus, 

 from Java and Celebes; S. tsftrbatus, from Borneo; and S. scrofa, 

 the boar, or common hog, whose domain extends, or did extend 

 before man had greatly narrowed its limits, over the greater part 

 of temperate Europe and Asia. This species, which was an early 

 inhabitant of Britain, as is indicated by the remains found in 

 the forest-bed (Post-Pliocene) of Norfolk, was completely exter- 

 minated in that region a number of centuries ago. Several 

 species of the genus have been found fossil in the Miocene and 

 Pliocene deposits of Prance, Italy, Germany, and Greece, and five 

 .are described from the Siwalik Hills of India, one of which, S. 

 Titan, is considered by Lydekker to have attained in extreme 

 specimens a height to the shoulder of forty-nine inches or more. 

 None of the genera of recent bunodont Artiodactyla are found 

 fossil in America with the exception of Dicotyles (peccary), which, 

 in association with a nearly related genus, Platygonus (also Plio- 

 cene), occurs in the Poat-Pliocene deposits. Closely related to the 

 last are the Miocene Thinohyus, Choenohyus, and Hyotherium 

 (Palseochoerus ?), the last a genus also abundantly represented in 

 Europe in deposits of both Upper Eocene and Miocene age. The 

 oldest representatives of the suilline tribe appear to be the forms 

 that have been described as Eohyus and Achsenodon (Parahyus ?), 



