50 THE NOTOG.EIC REALM. [CHAP. 



lian region 1 ; but it may perhaps with equal propriety be left 

 out of both till a further knowledge of its geology enables us to 

 determine its early history with more precision." 



Having now briefly surveyed the leading features of the terres- 

 trial mammalian fauna of the whole Notogaeic realm, 



Palaeonto- 



logicai History and discussed the relationship of the mammals of 

 the Austro-Malayan to those of the Australian region 

 (in the restricted sense of the term), we are in a position to enter 

 upon the consideration of the probable past history of Australia 

 and New Guinea, so far as the same group of animals is con- 

 cerned. Before doing so, it is, however, essential to state what 

 is known concerning marsupials from other regions of the world. 

 Here it may be premised that in regard to Australia mammalian 

 palseontological history is a total blank previously to the Pliocene 

 epoch ; while apparently but little is known even of that period, 

 the great majority of the fossil mammals of that country belonging 

 to the Plistocene epoch of the earth's history. As to the past 

 history of the mammals of New Guinea, we know absolutely 

 nothing ; and, as already mentioned, the same is the case with 

 regard to those of the Austro-Malayan islands. This, however, by 

 no means exhibits the whole depth of our deficiency of informa- 

 tion. Throughout the whole of eastern Asia, to say nothing of 

 Alaska and western Canada, we have no information whatever as 

 to mammalian life previous to the Pliocene era; while even in 

 that period our sole knowledge relates to a portion of northern 

 India and China. If, therefore, some of the modern types of 

 marsupials originated in eastern Asia from the older forms, the 

 blank in the palaeontological history of the group relates to just 

 the very countries where these animals might naturally be expected 

 to occur during the Tertiary period. While there is no record of 

 their existence in Asia, in Europe fossil Tertiary marsupials are 

 unknown at a later date than the upper Oligocene, and in North 

 America than the middle Oligocene, and the whole of those 

 hitherto discovered belong to the existing American group of 

 opossums. If, however, we were to infer from this that the whole 

 order (with the exception of that group) never existed in conti- 



1 Equivalent to the Notogaeic realm of this work. 



