HORN EXPKUITION SUMMARY. 181 



(2). A st'rius dufivcd tVoiii a cuiiufotioii with a lautl aix'a now lying to tli<_^ cast 

 (tf the continent (and connected also with the Papuan region) re{iresented l)y 

 J\Iicroj)iiyura and Acanthodiilus amongst lower forms and the stnithious birds 

 amongst vcrtebrata. 



(3). A scries derived from the Austro-Malayian region and including such 

 forms as the Paradiseidai and Megapodiid;f amongst birds, the true Rana amongst 

 amphibia, lizards such as Heteronota, Physignathus, etc., earthworms such as ti'ue 

 Periclueta, etc. 



(4). A large and important series derived from the south and indicating a 

 former connection with South America across Antarctic lands during a period not 

 later than the Miocene. These include, amongst manunalia, the ancestors of the 

 marsupialia, amongst amphibia, certain cystignathous frogs, and amongst fishes 

 Aphritis, Ilaplochiton, Galaxias, and the lamprey Geotria. 



Whilst there are considerable difHculties to be met — principally in the way 

 of explaining why certain forms are not present in Australia — if this connection 

 with South America l)e granted yet it nuist be allowed that with an increase in 

 our knowledge of the past and present distriljution of various forms the evidence 

 in favour of such a connection, as advocated by such writers as Forbes, Peddard 

 and HetUey on various grounds, has steadily increased, and, at the present time, 

 it is dilKcult to account for the distribution of the marsupials, and other forms 

 mentioned, in any other way. 



I have endeavoured above to show that the evidence is against the existence 

 of primitive marsupial types in tlu^ old western area of the continent when it was 

 separated from the eastern part, while the diminution of polyprotodonts as wc 

 pass north along the eastern side is strong evidenci; against their having enteied 

 Australia across the Torres Straits There has Ijeen, further, no direct connection 

 with the Asian continent since the east and west parts of Austialia became united 

 in late Cretaceous times, and we are therefore reduced to the supposition that tlii^y 

 reached Australia by way of America. 



The developmcJit and tlistribution of the existing fauna within the Australian 

 continent has been largely influenced by (1) the condition of the interior, and (li) 

 the existence of a high rangt^ running parallel to the south-east and eastern coast 

 lines and separating oil a narrow Ijut fertile and well-watered coastal strip of land 

 from a larger internal area, which since Pliocene times has been gradually 

 becoming more and more dry, witli the result that a climatic barrier has replaced 

 an earlier one formed by the Cretacc^ous sea. 



