HORN EXPEDITION — SUMMARY. 177 



Tho details with rcg.ii'd to tlie distiihutiou of the niemlicis of the various 

 groups represented in the central fauna have already hecn given in the summary of 

 zoological work. The general conclusion with regard to each may be stated briefly 

 as follows: — 



The Monotremata are represented by one species widely distributed over all 

 the continent e.vcept the north-we.st, the Marsupialia consist of species characteristic 

 of all the intei'ior but not including certain characteristic genera of the north-east 

 and the south-eastern coastal district including Tasmania, the Rodentia are clearly 

 derived from the east, the Inrds represent in the main a series wiilely flispersed 

 over the southern half of the continent, the Amphibia are very few in number and 

 arc closely allied to eastern species, the lizards represent both ubiquitous, northern 

 and perhaps especially western forms, whilst the Mollusca are on the whole western 

 forms with a slight ad-mixture of eastern and north-eastern l)ut with none of the 

 charactei'istic forms which have travelled from Tasmania northwards along the east 

 coast, while in the case of Microphyura, amongst the Mollusca and Acanthodrilus, 

 amongst the earthworms we have rare examples of forms whicli have evidently 

 travelled in from (he north-east by way of an ancient land connection, stretching 

 southwaids to the east of the present continent — a connection which gave to New 

 Zealand a certain admixture of such Australian types of plants as travelling fi-om 

 the west had reached this portion of the eastern coast, f It may at the same time 

 be taken for granted that there were then no marsupials present in the west or 

 centre or assuredly the path which could be traversed by a Microphyura or 

 Acanthodrilus could also be traversed by a mammal as it was, in all likelihood, by 

 the struthious birds. At this time, which probably coincided with the upheaval of 

 the Rolling Downs formation above the level of the Cretaceous sea, there must have 

 been a means of communication across from the noi-th-east to the centre and aw.-iy 

 to the west, which is a point of considerable importance in regard to the early 

 distribution of certain now distinctive Australian types. 



Speaking generally, theie is no evidence pointing to the fact that in the 

 case of the most important groups of Australian animals — the Monotremes 

 and the Marsupials — the old western part of the continent has any claim to the 

 title Autochthonian. If this were so, then we might expect to find, at all events 

 in the well-watered south-western portion, the lower group — the Monotremata — 

 well repi'esentcd, whereas the Platypus does not extend to West A.usti'alia and the 

 Echidna is as widely, in fact more widely, distributed ovei' the eastei-n portion. 



t W.allace, " Island Life," 1st Edit., p. 408. 



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