﻿INTRODUCTION. 5 



As the latter is still subsiding, there is accordingly evidence 

 of a still further extension of the land in this direction at 

 an earlier date. Wallace therefore concludes that Australia 

 must be regarded as an ancient continent of the Secondary 

 or early part of the Tertiary period, which is now gradually 

 decreasing in size, this diminution being indicated by the 

 gradual subsidence of New Caledonia and certain other South 

 Pacific islands. 



Till quite recently it was likewise believed that there were 

 no traces of Australian types of Marsupials in the Tertiary 

 rocks of the New World. Of late years, however, there have 

 been discovered in Patagonia a number of remains of large 

 carnivorous Marsupials with teeth and jaws of the same 

 general type as those of the Tasmanian Thylacine, and 

 apparently belonging to the same group. If this eventually 

 prove to be true, it would seem to point to there having 

 been some kind of land connection between Australia and 

 South America long after the period when the former country 

 was completely sundered from the rest of the Old World; 

 and it is noteworthy that there are certain other lines of 

 evidence pointing to the same conclusion. Be this, however, 

 as it may, it is certain that the Australian Marsupials, having 

 been isolated for countless ages from the rest of the world, 

 and thus not exposed to the competition of the higher types 

 of Mammalian life, have flourished and developed to an extent 

 which they could not possibly have reached in any other par*- 

 of the world under existing conditions. Even there, how- 

 ever, their present state of development is nothing to what it 

 was during the Pleistocene or latest geological epoch, since 

 we find at that period evidence of the existence of giant 

 Kangaroos and Wombats (to say nothing of certain extinct 

 forms which have left no living kindred), by the side of which 

 the largest existing species would appear almost dwarfs. The 



