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THE AMERICAN NATURALIST [Vol. XL 



seas or freshwater lakes (first surmised by Stuart) favored the 

 development of large marsupials. Conversely the rise of an 

 eastern coastal range was followed by diminished rain supply and 

 progressive desiccation of the interior region. 



Spencer observes:^ "The larger forms now extinct, such as 

 species of Diprotodon, Nototherium, Phascolonus, Macropus, 

 Protemnodon, etc., reached their greatest development in Pliocene 

 times and were characteristic of the eastern interior, spreading 

 southward round the western end of the Dividing Range into 

 Victoria. They do not seem to have reached the eastern coastal 

 district In Post-Pliocene times, with the increasing desicca- 

 tion of the whole central area they became extinct, though this, 

 extinction cannot be attributed wholly to the drying up of the land, 

 because in certain parts, such as Western Victoria, to which they 

 reached, the state of desiccation did not supervene; but at the 

 same time it may perhaps be justly argued that the desiccation 

 of the vast area of the interior was the largest factor in their extinc- 



The discovery \ IMlJ i of tlir urcat Lake Callaboima bone deposit 

 in the interior of South Aiisuuiia abundantly confirms the 'des- 

 iccation' theory. 1 )r. 11. ( '. .Stirling" describes this remarkable 



"'rinM-c is, lio\vcv(>r, compnisiition for the unpromising j)hysi('al 

 fratinv- of Lake Callabomiu in the fact that its bed proves to be a 



have apparently died where tiiey lie, literally, in hurHlre<k. The 

 facts that the l)ones of individuals are often md)roken, close to- 

 gether and. frecpiently. in their j)roper rehitive positions (ridr 

 pi A, fig the atiitiidc of many of thr bo.lie. and the character 

 of the matrix in uhi.h th^^ an> emhrdded, ne.-atiNe anv theorv 

 that they ha.,- been earrie.l thither floo.U. The probabiHty 



