BY R. M. JOHNSTON, F.L.S. 139 



country first existed as separate islands, and only became 

 united at a comparatively recent epoch. This is indicated 

 by an enormous stretch of Cretaceous and Tertiary forma- 

 tion extending from the Gulf of Carpentaria completely 

 across the continent to the mouth of the Murray River*. 

 During the Cretaceous period, therefore, and probably 

 throughout a considerable portion of the Tertiary epoch, 

 there must have been a wide arm of the sea occupying 

 this area, dividing the great mass of land on the west — the 

 true seat and origin of the typical AustraHan flora — from 

 a long but narrow belt of land on the east, indicated by 

 the continuous mass of Secondary and Palaeozoic forma- 

 tions already referred to, which extend uninterruptedly 

 from Tasmania to Cape York. Whether this formed one 

 continuous land, or was broken up into islands, cannot be 

 positively determined ; but the fact that no marine Tertiary 

 beds occur in the whole of this area (*) renders it probable 

 that it was almost, if not quite continuous, and that it not 

 improbably extended across to what is now New Guinea." 



. . . The eastern and the western islands . . . 

 would then differ considerably in their vegetation and 

 animal life. The western and more ancient land already 

 possessed in its main features the peculiar AustraHan flora, 

 and also the ancestral forms of its strange marsupial fauna, 

 both of which it had probably received at some earlier 

 epoch by a temporary union with the Asiatic continent 

 over what is now the Java Sea. Eastern Australia, on the 

 other hand, possessed only the rudiments of its existing 

 mixed flora, derived from three distinct sources. 



" Some important fragments of the typical Australian 

 vegetation had reached it across the marine strait, and 

 had spread widely, owing to the soil, climate, and general 

 conditions being exactly suited to it ; from the north and 

 north-east a tropical vegetation of Polynesian type had 

 occupied suitable areas in the north ; while the extension 

 of the Tasmanian peninsula, accompanied probably, as now, 

 with lofty mountains, favoured the immigration of south 



* The discovery at Table Cape and elsewhere of the marine beds of Eocene 

 age, similar to those of the Murray, indicate the extension of this old 

 Tertiary sea to Northern Tasmania. (R. M. J.) 



* The Heathy Valley limestones of Tertiary age on Flinders' Island, and 

 other marine deposits on several of the connecting islands in the eastern 

 portion of Bass' Strait, indicate the probable occurrence of one or two 

 minor straits, as at prosent. (R. M. J.) 



