INTRODUCTION. XI 



Victorian fauna is divisible into three sections a northern, southern, and 

 western desert one. 



Consequently Victoria is a confusing term when cited as the locality of 

 any bird, and this refers to most other State names, though not so well marked 

 in so circumscribed an area. The most famed endemic Australian birds, such 

 as the Emu and Lyre Bird, are equalled in zoogeographic interest by less 

 well-known forms which are too numerous even to mention here. Each 

 provides an essay in itself as to its distribution, but it may here be asserted 

 that all are confined to the southern part of Australia, both east and west. 

 At the present time some show discontinuous range through the intervention 

 of the great central desert. Some, apparently definitely restricted and evolved 

 in this southern area, have again spread northwards and repopulated the 

 areas from which their ancestors ranged southwards. At the same time 

 the succeeding fauna has extended its limits and penetrated into Australia 

 even to the southernmost limits, but scarcely ever reaching Tasmania. It is 

 this complex which makes the study so interesting, as the facts are so obvious 

 that these succeeding migrations can almost be defined with unfailing accuracy. 

 However, we will suggest these movements, without dealing in great detail, 

 thus : Palseontologically, we have not the data to assert a definite period, 

 but we can fix an early migration from the north which overran Australia 

 before the severance of the Bassian Isthmus and whose members quickly 

 developed in a degenerate manner through lack of inimical opposition. The 

 separation of Tasmania took place after degeneration had set in, so that the 

 island forms were left as isolated unprogressives. On the mainland, changing 

 conditions compelled a certain amount of competition, and we find the con- 

 temporaries of the island species a little more advanced on the mainland. 

 Some of them even, adapting themselves as the situations demanded, progressed 

 so that they could not only defend themselves but take the offensive, and 

 these, being barred from any advance southward, attempted a northward 

 dispersal. These constitute the bulk of the Australian Ornis and include 

 the majority of the endemic genera and species. From the observed data 

 w r e conclude that after the division of Bass Straits another immigration from 

 the north took place and this also succeeded in overrunning Australia, but 

 did not cross the Straits into Tasmania. It is probable that the competi- 

 tion between these two elements the invaders and the settlers resulted in 

 the extermination of many of the weaker forms of the latter, a few resisting 

 and being now recognised in such a survival as Alrichornis. The stronger 

 settlers, of course, continued their progress accumulatively under the stress 

 of the stronger newcomers in order to retain their places. The new 

 immigrants in their turn soon accustomed themselves to the environment 

 end became adapted to the lack of great stress, and a few of these again evolved 

 the role of pioneer and perforce had to retrace their ancestors' steps into the 

 north. In these attempts probably many more failed than succeeded, and 

 we have only record of the successes. This migration can be seen throughout 

 Australia in the form of differentiated species of prevailing northern genera. 



