ZOOGEOGRAPHICAL REGIONS 213 



rapid. Here we find the highest mammals and the 

 most specialized birds. Where the tropical forest is 

 dense a few primitive forms linger, and some also have 

 been saved by isolation, e.g. in Madagascar. But as 

 a general rule the primitive forms have been crushed 

 out of existence by higher forms. No marsupial (save 

 one opossum in North America) now lives within this 

 great area, and no monotreme. No primitive reptile-, 

 like the Hatteria of New Zealand, points us back to an 

 earlier age. Here and here alone do we get the highest 

 of the primates apart from man — the anthropoid apes 

 and the dog-faced baboons. Here and here alone do 

 we get the highest and most specialized of the ungulates, 

 and so on. 



For this great area various names have been pro- 

 posed. Thus it has been called Arctogaea, or the 

 Northern World, because of its mainly northern position, 

 though Africa extends far to the south. 



In regard to the boundaries of this realm it may be 

 said that over much of the area they are formed by 

 the sea. In two regions, however, difficulty occurs. 

 One is in the south-east, where a boundary line has to 

 be drawn through that mass of islands which stretches 

 between Further India and the northern shores of 

 Australia. Wallace drew the line which separates his 

 Oriental (or Indian) region and the Austrahan region 

 between the islands of Bali and Lombok. A narrow 

 but deep strait separates these islands, and Wallace 

 believed that all the islands to the east of this strait 

 (Wallace's line) possessed faunas with a distinctively 

 Australian faoies, while those to the west had faunas of 

 Indian type. Recent detailed research has thrown 

 some doubt upon this statement. A mingling of 

 faunas certainly occurs in this region, and any hard 



