52 THE HORSE. 



that they share the honors with Hyomoschus or Dor- 

 catJierium* of being the oldest living mammalian 

 form. Such remains of Miocene and Pliocene age 

 have been found in France, Germany, and England 

 (Suffolk red crag). They appear, however, to have 

 become extinct in Europe before the Pleistocene 

 period, as none of their bones or teeth have been 

 found in any of the caves or alluvial deposits in 

 which those of elephants, rhinoceroses, and hippo- 

 potamuses occur in abundance ; but in other regions 

 their distribution at this age was wider than at 

 present, as they are known to have extended east- 

 ward to China, and westward over the greater part of 

 the southern United States of America, from South 

 Carolina to California. Lund also distinguished two 

 species or varieties from the caves of Brazil. Thus 

 we have no difficulty in tracing the common origin 

 of the now widely separated American or Asiatic 

 species. It is, moreover, interesting to observe how 

 very slight an amount of variation has taken place 

 in forms isolated during such an enormous period of 

 time. This may be owing to the extreme similarity 

 of the conditions of existence in a Brazilian and a 

 Malayan forest. 



* A small Artiodactyle, somewhat intermediate in struct- 

 ure between a deer and a pig, found living in Western Africa 

 and fossil in deposits of Miocene age in Germany. 



