62 THE NOTOG^IC REALM. [CHAP. 



That Notogaea, as typified by the Australian region, is entitled 

 to form one of the three primary zoological divisions of the globe, 

 the distinctness of its mammalian fauna from that of any other 

 area, not only at the present day, but likewise during the Plisto- 

 cene, and probably also the Pliocene epoch, amply demonstrates. 

 The inclusion within the same realm of the Polynesian region, 

 which evidently never had such a close connection with south- 

 eastern Asia during the time that area was mainly populated with 

 marsupials, is justified partly on account of its containing more 

 or less similar types of birds, and partly by the practical absence 

 of terrestrial mammals. On the other hand, the Austro-Malayan 

 region, which is really a kind of zoological No-man's-land, is 

 placed within the limits of the same great realm more as a matter 

 of convenience than anything else, although it is undoubtedly 

 sharply differentiated from the Oriental region by Wallace's line. 



In conclusion, a few lines may be devoted to showing that 

 certain other groups indicate that the vertebrate fauna of Notogaea, 

 as a whole, has had a northern origin. Among the lizards, the 

 family of iguanas (IguanidcB], which in this realm occurs only in 

 the Fiji and Friendly Islands, is represented in a fossil state in 

 the Oligocene beds of France ; while the gigantic extinct monitor 

 ( Varanus priscus) of the Australian Plistocene appears to have its 

 nearest ally in the smaller V. sivalensis of the Pliocene of northern 

 India. The Notogseic Chelonians, which are confined to Australia 

 and New Guinea, all belong to the side-necked group (Pleurodira) 

 of the order, and are represented by the families Chelyidce. and 

 Carettochelyidce, the latter containing only a single species from 

 the Fly River. Now, although none of the Australian genera have 

 been detected in the northern hemisphere, the side-necked chelo- 

 nians, as shown in the next chapter, were abundantly represented 

 there during the early Tertiary and Secondary epochs ; and it 

 is a remarkable fact that an extinct genus believed to be allied 

 to Carettochelys occurs in the Eocene of northern India. Although 

 from their aquatic, and sometimes partially marine habits, the 

 crocodiles are of less importance than some other groups from a 

 distributional point of view, yet it is noteworthy that the single 

 representative of that group ( Crocodilus porosus] inhabiting Noto- 

 gaea (where it is found in North Australia, the Solomons, and 



