118 president's address — SECTION D. 



of Australia — a submergence which, as before said, finally 

 separated off Tasmania, 



When once developed the diprotodont forms rapidly spread 

 south along two paths, one to the east and then to the south 

 of the Divide, another to the west and then to the north of 

 the Divide. Though not of course perfectly distinct from 

 one another, certain widely-spread forms occurring in each, 

 still, speaking generally, we may say that the east and south 

 (using these terms relatively to the Divide) gave rise to the 

 coastal diprotodonts in New South Wales and Victoria, 

 whilst the west and north forms spread westwards into S. and 

 W. Australia, though their migration was considerably 

 hindered by the barriers mentioned above. 



It was most probably whilst Tasmania was gradually 

 being separated off from the mainland, and when it retained 

 a relatively small connection by a neck of high land passing 

 across what is now the east of Bass Straits, that the 

 migration of the diprotodont forms was taking place down the 

 east coastal district. Hence it was that comparatively few 

 crossed into Tasmania, a strikingly smaller proportion of 

 diprotodont than of polyprotodont forms being present in the 

 Island. 



We must conclude from the mammalian fauna that there has 

 been no absolute land connection between south-east Australia 

 and Tasmania since practically the end of the Tertiary Period 

 or early in Pleistocene times, as otherwise it would be 

 impossible to account for the absence, not only of the dingo, 

 but of the large and specialized diprotodont fauna of which 

 the Pleistocene Period saw the rise and fall upon the main- 

 land. 



If tables of the comparative distribution of the genera and 

 species of polyprotodont and diprotodont forms respectively 

 be drawn up for the various parts of Australia, including 

 Tasmania, we find in them, I think, evidence of the truth of 

 the three main suggestions included in the above account. 

 These are : — 



(1.) That the primitive polyprotodont fauna entered by 

 the north-west rather than by the north-east part 

 of the continent, sj^read thence south and then 

 across to the east. 



(2.) That the diprotodonts had their origin in the 

 Euronotian region and spread thence southwards 

 and westwards. 



