HOltX EXPEDITION— SUMMARY. 185 



111 liis recently published work uii tlie "Geographical History of iVIaniiiials,"* 

 Mr. Lydekker adopts the more generally accepted theory that the primitive 

 marsupial fauna entered Australia by way of south-east Asia ; though he grants 

 the importance of tlu^ discovery of dasyuroid niarsui)ials in the Tertiary rocks of 

 Patagonia as pointing towards the existence, at some period, of a direct conuiiuni- 

 cation between the south of America and Australia, and points out the importance 

 of the determination liy Messrs. David and Smeeth of the nature of the rocks 

 brought back in the recent cruise of the " Antarctic," l)y Mr. Borchgrevink as 

 indicating a continental area. In fact Mr. Lydekker makes tlie following 

 important statement: — "It may be observed that it appears impossible to 

 adequately explain the presence of a Notoga-ic element in the fauna of Net)g!ea 

 without the aid of some form of southern land connection ; although there is not 

 sufficient evidence to show in what latitude such connection (or connections) 

 existed. :J: 



Mr. Lydekker is of opinion that the original immigration of early polyprotodont 

 forms took place across what is now New Ciuinea and so into north-east Australia, 

 and there " where they have since been isolated from any serious competition with 

 the higher mammals, they tloui'ished and developed to a degree which they could 

 not possibly have attained to in any other part of the world under existing con- 

 ditions."* 



At the same time Mr. Lydekker grants that the evolution of the Diprotodonts 

 took place within the limits of the Australian continent and that therefore the 

 Cuscuses — the most typical Papuan marsupial — are to be regarded as innnigrants. 



Now it is the Papuan region firstly and the north-east portion of Austialia 

 secondly, which are remarkal)ly poor in Polyprotodonts ; such as the Papuan region 

 possesses arc conlined to three genera, Dasyiirus (one species), /•'t'/-rt/;/t'/fj' (six species), 

 riiascologale (five species), which, it may be remarked, are the most widely 

 distributed of all the Australian Polyprotodonts and the most capaljle of adapting 

 themselves to the arid climate of the interior, or the more genial coastal climate 

 from cool Tasmania in the south to tropical New Guinea in the north. On the 

 supposition that N(!W Guinea lay in the line of migration of the primitive marsupials 

 it is an inexplicable fact that here where they can and do live in small numbers, 

 free from competition with higher forms, we have still so little trace of Polyproto- 

 donts and not a single form which is not widely dispersed over the continent. The 



* Cainbridyu Geo^'riijihical Serius, 18'.)ti 

 t hoc. cil., )). 127. 

 X Loc. cit., p. 01. 



