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STUDY OF THE ODONATA OF TASMANIA IN 

 RELATION TO THE BASSIAN ISTHMUS. 



By R. J. Tillyard, M.A., F.E.S., Science Research Student 

 in the University of Sydney. 



Introduction. 



The Bassian Isthmus is the name given to that portion of land, 

 now sunk beneath the sea, which once connected Tasmania with the 

 mainland of Australia. Although all scientists are agreed on the 

 previous existence of such a connection, yet there is not, so far, 

 sufficient evidence to enable us to say, definitely and precisely, 

 when, where and how long it existed, and at what period of past 

 time it broke down. 



A short summary of the opinions expressed on the point will 

 perhaps make the position clear. 



Professor Baldwin Spencer* (1892), on the evidence afforded by 

 the Mammalia, concluded that "at some period during Tertiary 

 times, .... and comparatively early in the period, Tasmania began 

 to be gradually separated off from the mainland. . . . When Tas- 

 mania became separated off, it contained a series of forms identi- 

 cal, so far as genera are concerned, with those of what is now Vic- 

 toria, and in species almost identical with those of Southern Vic- 

 toria." And again : "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 also of the large and specialised Diprotodont fauna, of 



* Report Aust. Assoc. Adv. Sc, Hobart, 1892. pp.117, 118. 

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