120 president's address — SECTION D. 



land of which New Guinea now forms part and yet New 

 Guinea has the least, and Queensland the next least, per- 

 centage of forms present. On the other hand the greatest 

 percentage of genera is possessed by South Australia and 

 West Australia. Now there can be httle doubt but that the 

 struthious birds entered by the north east, and in the case of 

 these we find that this portion is the richest both in genera 

 and species. 



The conclusion that can be apparently drawn from the 

 comparative distribution of the Polyprotodonts is that they 

 did not enter by way of the north east but that, on the 

 contrary, this was the last part which they reached. Their 

 comparatively very equal distribution over the whole con- 

 tinent and Tasmania, except this one part, and their strong 

 development in South and West Australia seem to indicate 

 that during the time of migration of these, which are 

 undoubtedly, the more primitive of the two marsupial groups, 

 there did not exist such distinct barriers of climate or 

 geographical features as existed later on, though in all 

 probabiUty during their early distribution the Cretaceous 

 sea was encroaching on the land. Further still, their strong 

 relative development in Tasmania indicates that this then 

 formed simply a southern projection of the mainland. 



It might possibly be suggested that though the forms 

 entered by the north east the small percentage of Queens- 

 land polyprotodonts is due to extinction following upon sub- 

 sequent competition of the diprotodont forms. The answer 

 to this is that Victoria and New South Wales have very 

 nearly the same percentage of diprotodont forms (exactly 

 the same in genera) and yet competition has not by any 

 means affected their polyprotodont fauna in the same way. 



If we now compare the tables giving the percentage of 

 diprotodont forms present in tlie various parts we find a 

 very different result. The order being Queensland, New South 

 Wales, Victoria (all three of which are comparatively rich), 

 then a considerable break and South and West Australia 

 nearly equal, then another larger break still and Tasmania. 



These results can, I think, only be interpreted to mean one 

 thing and that is, that the Diprotodont fauna arose and 

 reached its highest development in the subtropical regions of 

 the Euronotian province, that is, in South Queensland and 

 northern New South Wales. Thence it spread easily north- 

 wards through Queensland and so to New Guinea and the 

 islands, then becoming separated off and southwards partly 



