374 PALAEONTOLOGY AND EVOLUTION xi 



The fact that this immense fauna of Miocene 

 Arctogsea is now fully and richly represented only 

 in India and in South Africa, while it is shrunk 

 and depauperised in North Asia, Europe, and 

 North America, becomes at once intelligible, if we 

 suppose that India and South Africa had but a 

 scanty mammalian population before the Miocene 

 immigration, while the conditions were highly 

 favourable to the new comers. It is to be supposed 

 that these new regions offered themselves to the 

 Miocene Ungulates, as South America and Australia 

 offered themselves to the cattle, sheep, and horses 

 of modern colonists. But, after these great areas 

 were thus peopled, came the Glacial epoch, during 

 which the excessive cold, to say nothing of depres- 

 sion and ice-covering, must have almost depopu- 

 lated all the northern parts of Arctogaea, destroying 

 all the higher mammalian forms, except those 

 which, like the Elephant and Rhinoceros, could 

 adjust their coats to the altered conditions. Even 

 these must have been driven away from the 

 greater part of the area; only those Miocene 

 mammals which had passed into Hindostan and 

 into South Africa would escape decimation by such 

 changes in the physical geography of Arctoga3a. 

 And when the northern hemisphere passed into its 

 present condition, these lost tribes of the Miocene 

 Fauna were hemmed by the Himalayas, the 

 Sahara, the Red Sea, and the Arabian deserts, 

 within their present boundaries. 



