DISTRIBUTION 



131 



independently of the mouth and gullet, thus averting the danger of 

 suffocation while the milk is passing down the latter passage. 



Distribution. — The existing species of Marsupials are, with the 



region, 



forming 



->v 



the chief 



Fig. 35. — Front view of skull of Sarcophilus ursinas, showing polyprotodont and carnivorous 

 dentition (Quart. Journ. Geol. Soc. vol. xxiv. p. 313). 



exception of one family (the Didelphyidce), limited in geographical 

 distribution to the Australasian 

 mammalian fauna of Australia, 

 New Guinea, and some of the 

 adjacent islands. The Didel- 

 phyides are almost purely Neo- 

 tropical, one or two species 

 ranging northwards into the 

 Nearctic region. Fossil re- 

 mains of members of this 

 family have also been found in 

 Europe and America in strata 

 of the Eocene and early Mio- 

 cene periods ; and it is probable 

 that at least many of the poly- 

 protodont Mesozoic mammals 

 noticed in Chapter IV. are 

 referable to the Marsupialia. 



Classification. — In dividing 

 the Marsupials into minor 

 groups, it may be observed 

 that one of the most obvious 

 distinctive characters among 

 them is derived from the form 



Fig. 36. — Front view of skull of Koala (Phas- 

 colarctics cinereus), showing diprotodont and 

 herbivorous dentition (Quart. Journ. Geol. Soc. 

 vol. xxiv. p. 313). 



and arrangement of the teeth. 

 1 Including the transitional Austro-Malayan region. 



