1322 CLASS MAMMALIA. 



a triangular section, and received into a notch in the upper jaw, as 

 in the Peccaries. The typical forms have only three premolars, but 

 in others, which it has been proposed to separate generically as 

 Bothrolabis, there are four of these teeth. Allied, or probably iden- 

 tical forms have been described as Thinohyus and Perchoerus, the 

 former having four premolars. The existing South American genus 

 Dicotyles includes the well-known Peccaries, and has the dental 



2 1 "3 3 



formula I. -, C. -, Pm. -, M. -. The structure of the small 



3 i 3 3 



canines has been already mentioned ; the last upper premolar has 

 four columns like the true molars (fig. 1196) ; while the third upper 



Fig. 1196. — Grinding surface of the right upper cheek-teeth of a Peccary {Dicotyles 

 labiatus). (After Giebel.) 



true molar, which comes into use before the first is worn, has no 

 distinct third lobe. In the pes the phalangeals of the fifth digit are 

 aborted. Remains of two existing and one much larger extinct 

 species of this specialised genus are found in the Pleistocene de- 

 posits of the Brazilian caves ; while large Peccaries also occur in 

 the Pliocene of the United States and the Pleistocene of Mexico, 

 which have been described as Piatygonus, but may be included 

 in the type genus, although they have rather simpler premolars. 



Family Chceropotamid^:. — The true molars of this extinct 

 family are intermediate in structure between those of the Suidce and 

 Anthracotheriidce ; having in the upper jaw very broad and short 

 crowns, which carry five columns arranged as in the latter family. 

 The premolars, although somewhat compressed, are not secant, and 

 may be of very large size. In the two best known European genera 

 there is a diastema between the first and second upper premolars. 

 The mandible has no descending flange at the angle. 



One of the most pig-like members of this family is the genus 

 Cebochoerus, comprising animals of the size of Hyotherium, which 

 have been considered by some as allied to the Lemuridce, although 

 there is little doubt that their true relationships are with the present 

 group. They apparently possessed the full typical number of teeth, 

 which (especially in the lower jaw) present a great resemblance to 

 those of Hyotheriu?n ; and it is highly probable that they are closely 

 related to the ancestor of that genus. Cebochoerus is represented by 

 several species in the Upper Eocene of France ; but the form re- 



