president's address — SECTION D. 113 



forms have come into competition the Dingo has driven out 

 its two immediate competitors which can only now exist 

 where it is absent; whilst there are clear signs that the 

 remaining form which does not so directly come into com- 

 petition with it is now being reduced in numbers and may 

 ultimately have to give way. 



General conclusions with regard to the Origin of the Mono- 

 treme and Marsupial Fauna of Australia and Tasmania. 



The great classical work of Wallace, it is scarcely neces- 

 sary to say, marked an epoch in our knowledge and under- 

 standing of the origin and relationships of the Australasian 

 fauna and flora. Subsequent workers can follow in his foot- 

 steps and as fresh knowledge is acquired can fill in 

 details which verify, or may to a certain extent modify, his 

 conclusions. 



Thus, with regard to his generalisations concerning 

 Australia, Professor Tate has pointed out, m his address to 

 this Section at the opening meeting of the Association in 

 Sydney, that Wallace was mistaken in his assumption that 

 an old Tertiary sea extended in a wide gulf from north to 

 south through central Australia. Mr. Wallace recognised 

 tiiat for some long period of time the south-western part of 

 Australia, that is, practically, the Autochthonian region of 

 Professor Tate, must have been isolated from the eastern or 

 Euronotian region. That this has been the case, though 

 not apparently quite in the way suggested by Wallace, 

 Professor Tate himself points out, and to the latter we 

 owe the important demonstration of the probable manner 

 of isolation of the Autochthonian region. I may here express 

 my indebtedness to the facts and suggestions contained in 

 Professor Tate's important contribution to our knowledge of 

 the distribution of living forms in Austraha. 



We will now deal with the main points of interest in the 

 Tasmanian fauna in its relationship to other parts. 



The most interesting of these is naturally concerned with 

 the Prototherian and Metatherian mammals. Of late years 

 our knowledge of the fossil remains of primitive mammals has 

 been vastly increased and various points concerned with 

 their ancestry and relationships have been elucidated by such 

 workers as Cope, Marsh, Osborne, Baur, Lydekker, and 

 Oldfield Thomas. One of the most important discoveries is, 

 perhaps, that of the presence of teeth in the young form or 

 platypus, first discovered by Poulton, whilst to Oldfield 



