DISTRIBUTION OF MAMMALIA IN TIME. 645 



in which continent no indigenous horse existed at the time of 

 its discovery. 



Of the Rhinoceridce, a hornless form (Acer other ium) occurs in 

 Miocene and Pliocene strata ; but the best-known fossil species 

 is the two-horned woolly Rhinoceros (J?. tichorhinus}. This 

 curious species occurs in Post-pliocene deposits, and must have 

 ranged over the greater part of Europe. It was adapted to a 

 temperate climate, and, like the Mammoth, possessed a thick 

 covering of mixed wool and hair. This has been demonstrated 

 by the discovery of a frozen carcass in Siberia. 



Of the Hippopotamidtz, the earliest-known species is the 

 Hippopotamus major of the Pliocene period. This form agreed 

 in all essential respects with the living H. amphibius of Africa, 

 but it must have ranged over the whole of Southern Europe. 

 Hexaprotodon, of the Tertiary deposits of the Siwalik Hills of 

 India, is a sub-genus of Hippopotamus proper, and had six 

 lower incisors. 



Of the Suida, or Pig tribe, various extinct forms are known 

 from the Eocene and Miocene rocks, where the family is 

 represented by the genera Chczropotamus^ Anthracotherium, 

 Hyopotamus, and Hippohyus. 



Fig, 277. The Irish Elk (Megaceros Hibernicus). 



As regards the past existence of the Ruminants, the Cenida 

 or Stag tribe, is represented, for the first time in the Miocene 

 period, by the genus Dorcatherium. The best-known species, 

 however, of this family is the Megaceros Hibernicus, or so-called 

 Irish Elk (fig. 277), which is not a true Elk, but is intermediate 

 between the Fallow-deer and Reindeer. A fossil Camel (C. 



