566 MANUAL OF ZOOLOGY. 



not older than the Pliocene or Post-pliocene. At this latter 

 period England alone possessed four oxen viz., the Lithua- 



Fig. 218. The Irish Elk (Megaceros Hibemicus). 



nian Aurochs (Bos bison or Bos priscus\ the Wild Bull or 

 Urus (Bos primigenius), the Bos antiquus, and a small aboriginal 

 species, the Bos longifrons, believed by Owen to be " the source 

 of the domesticated cattle of the Celtic races before the Roman 

 invasion." 



Order VII. Hyracoidea. This little order, represented at 

 the present day by no more than the single genus Hyrax, is 

 not known to have any fossil representatives. 



Order VIII. Proboscidea. This order, including no other 

 living forms than the Elephants, came into existence in the 

 Miocene period, where it is represented by all its three sec- 

 tions, Deinotherium, Mastodon, and Elephas. 



The Deinotherium (fig. 202) was a gigantic Miocene Mam- 

 mal, probably something like the living Elephants, but having 

 no incisors in the upper jaw. In place of these, the lower jaw 

 was furnished with two long tusk -like incisors, which were 

 bent downwards. 



In most essential respects the Mastodons (fig. 219) resemble 

 the Elephants, but the molar teeth were furnished with nipple- 

 shaped eminences. Usually there are two tusk-shaped upper 

 incisors, but sometimes lower incisors are present as well. 

 Four Mastodons occur in the Miocene of Europe, and three 

 in that of India. 



No Elephant has yet been discovered in the Miocene Rocks 



