1320 CLASS MAMMALIA. 



of development varies greatly ; and these teeth do not come into 

 use until the first molar has been well worn. The anterior pre- 

 molars are compressed, and there is no diastema between the first 



and the second. The upper 

 premolars are simpler than the 

 true molars, and there is con- 

 siderable difference in the num- 

 ber of accessory tubercles de- 

 veloped in the latter ; those 

 species in which these are most 



Fig. 1194.— The third right lower true molar numerous showing a more COm- 



of Sus cristatus ; India, a, d, Middle columns . , 



of talon. plex pattern on the worn 



crowns. The molars of some 

 of the earlier forms approximate to those of Hyotherium. 



The species with the most complicated molar structure are S. Falconeri 

 of the Pliocene of the Siwalik Hills, S.phacochceroides of the Pliocene of 

 Algeria, S. karmdiensis of the Pleistocene caves of Madras, and the 

 living Indian S. cristatus (fig. 1194), which is also found fossil in the 

 same caves ; the last lower true molar of the first-named species making 

 a decided approach to that of Phacochaerus. In the European Wild- 

 boar, which is found fossil as low down as the Norfolk Forest-bed, the 

 hind lobe of the last molar is of moderate complexity. S. titan, and S. 

 giganteus of the Siwalik Hills of India, together with S. antiquus, S. 

 erymanthius, and S. major of the Lower Pliocene of Europe, are large 

 species with comparatively simple molars ; the first being the largest 

 known species, and fully equal in size to a Tapir. S. hysudricus of the 

 Siwalik Hills, S. palceochoerus of the Lower Pliocene of Eppelsheim, and 

 S. choeroides, which has been recorded from France and the Middle 

 Miocene of Tuscany, are small species with simple molars like those of 

 the living S. andama?iensis, to which they may be allied. S. arvemensis 

 of the Upper Pliocene of France is closely related to the living African S. 

 {Potamochcerus) africanusj while in the small .9. punjabiensis of the 

 Pliocene of north-western India we probably have the direct ancestor of 

 the Pigmy-hog (S. salvanius) of the terai-lands of Nipal. No represen- 

 tatives of the genus occur in America ; and S. ckazroides seems to be the 

 earliest species. 



Here it will be convenient to notice the African Wart-hogs 

 (Phacochcerus) which appear to be related to some of the specialised 



fossil species of Sus. The dental formula is I. -, C. -, Pm. - 



(2-3) 1 3 



M. -, but the whole of the teeth with the exception of the canines 



3 

 and the last true molars may be lost in the adult, thus presenting a 

 very remarkable instance of extreme specialisation. The last true 

 molar is a very peculiar tooth, consisting of a great number of tall 

 agglomerated columns, or denticules ; but a marked approach to 

 this structure is presented in some of the species of Sus from the 



