138 THE VICTORIAN NATURALIST. 



to represent the probable extension of the old land, we shall see 

 that it would give us a wide additional area, and form a continent 

 which, even if the greater part of tropical Australia were sub- 

 merged, would be sufficient for the development of a peculiar and 

 abundant flora. This elevation of 6,000 feet would change the 

 whole country, including the deserts in the interior, into mountain- 

 ous and well-watered regions. Close following the extinction of 

 the Cretaceous epoch was another submergence during deposition 

 of old Tertiary bed. Besides this, the Pliocene Tertiary beds of 

 median Australia were due to existence of great inland sea. Pro- 

 fessor Tate claims for the Eremian region of this period a very 

 much larger rainfall than it has now, and appeals to evidence of 

 waterless large river channels, contracted and saline lake basins, 

 and nature and deposition of sand ridges. But, from whatever 

 cause, since Pliocene times Central Australia has been drying up,, 

 and the present barrier of climate to the migration of plants has 

 simply replaced one different in kind — that is, arms of the sea and 

 inland seas. 



The conclusions drawn from a study of the flora are that — 

 (i) The Autochthonian region, with its highly specialized 

 Australian types and its long-continued isolation, is of greater 

 antiquity. (2) That Euronotian flora was modified during early 

 Tertiary times by primitive European types, and has received in 

 recent times greater accession of Asiatic races. 



II. Fauna. — In case of the fauna we find the converse of the 

 vegetation, for morphological variety is greatest in the Euronotian 

 region. 



Mammals. — The most striking feature is the almost entire 

 absence of the higher mammalia. Mammalia may be divided 

 into three groups — (i) Monotremes, (2) Marsupials, and (3) 

 Eutheria. The Eutheria absent in Australia, except for bats, 

 rats, and mice. In New Zealand there are no mammals at 

 all ; none of the various marsupials of Australia and Tasmania are 

 present. Birds are the highest vertebrates, (i) Montremes are 

 confined to Australia, and consist of two rare and remarkable 

 forms, Platypus and Echidna, probably the descendants of some 

 of those earlier developments of mammalian life, which in every 

 other part of the globe have long been extinct. (2) Marsupials, 

 found nowhere else on the globe, except a single family, the 

 opossums of America. The Marsupials are wonderfully 

 developed in Australia where they exist in most diversified forms 

 adapted to diliferent modes of fife — some carnivorous, some 

 herbivorous, some arboreal, some terrestrial. They are divided 

 into two large groups — i. Diprotodontici ; ii. Polyprotodontici. 

 i. Diprotodontia. — These are rarely carnivorous. They have 

 three incisors above and one below. They include Kangaroos, 

 Wallaby, Tree Kangaroos of New Guinea and Queensland, 



