30 



GUIDE TO THE FOSSIL MAMMALS AND BIRDS. 



Pier-case 

 13. 



Fig. 18. — Palatal view of skull (A), symphysis of lower jaw (B), and grinding 

 surface of molar tooth (C) of an extinct Hippopotamus (Hvgpcypota/rrms 

 sivalensis), from the Lower Pliocene of the Siwalik Hills, India ;^A 

 and B one-eighth nat. size, G one-half nat. size. (Pier-case 12.) 



The true pigs, or Suidse, have always been confined to 

 the Old "World, and the oldest known species is Sus chceroides, 

 from the Middle and Upper Miocene of France and Italy. 



Among the fossil remains 

 of this family in Pier- 

 case 13 may be noticed 

 skulls, jaws, and teeth of 

 the wild boar from England 

 and Ireland ; some fine 

 skulls and jaws of the large 

 Sus erymanthius, from the 

 Lower Pliocene of Pikermi, 

 Greece; pieces of skulls 

 and jaws of other extinct 

 species from the Lower 

 Pliocene of the Siwalik Hills, India; and similar remains 

 of Hippohyus sivalensis, a pig from the Siwalik Formation 

 with deepened grinding teeth rendered very effective by the 

 crimping of their enamel. 



Fig. 19. — Grinding surface of third 

 right lower true molar tooth of an 

 existing Pig (Sits cristatus), from 

 India; nat. size. a, d, middle 

 columns of talon of tooth. 



