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ON THE STUDY OF ZOOGEOGRAPHTCAL llEGTOXS 

 BY MEANS OF SPECIFIC CONTOURS. 



With an application to the Odoxata of Australia. 



By R. J. TiLLYAHD, M.A., F.E.S. 



(Nkw South Wales Government Research Student in 



BlOLOfa' AT THE UNIVERSITY OF SVDNEY.) 



(Plate i., and Transparencies 1-3.) 



It can scarcely be denied that the science of Zoogeography is 

 in a somewhat unsatisfactory condition, and that great difhcnlties 

 exist both in the following out of lines of research and in the 

 drawing of general conclusions. 'J'his is not to be wondered at, 

 when we realize that the present distribution of the fauna and 

 Hora of the earth has been brought about by the acting together 

 of so many conflicting conditions, continually cliangiiig through- 

 out immense!}" long geological periods; and that the task of 

 re-picturing or re-constructing these conditions is in itself a most 

 baffling one, owing to the very fragmentary evidence still pro- 

 served to us. 



Under these circumstances, any method which may promise to 

 yield good results, and to give us a clearer view of the problem 

 in hand, is worthy of a trial. The author, therefore, offers the 

 method explained in this paper, with the intention neither of 

 ousting any of the already approved methods of study, nor of 

 proclaiming the discovery of a panacea for the difficulties known 

 to exist; but rather with the purpose of presenting the subject 

 in a new light, in which, it is hoped, certain facts may be made 

 to stand out in bolder relief than they have hitherto done. 



It is now generally admitted that the six main zoogeographical 

 regions, as originally proposed by Sclater, and modified by 

 Wallace, are valid subdivisions of the land-surface of the earth, 

 as far as its fauna and flora are concerned. But though these 

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