18() HORN EXPEDITION — SUMMAIU'. 



poverty of Pulyprot(xloiit life can scarcely be attributed to tlieir liaviuif been 

 (Iii\cii south foi" which tlien^ is no reasou whatever or to competition (certainly 

 not with Diprotodonts, as in .Vustralia the two groups t'xist in large numbers side 

 by side), whik' it can be most naturally explained liy the fact that the Papuan was 

 th(^ last and not tiie first land of the Australian region to be r'cached Ijy the 

 marsui)ial fauna. 



Mr. Lydekker regards the occurrence of Australian types of Rats in the 

 Piiillij)ines as of " the utmost importance in respect to Australia ha\ing received 

 its mannnalian fauna from south-eastern Asia,"" though at tlie same time he 

 states that they must be regarded as comparatively recent innnigrauts and " are 

 of comparatively small size, so that it is possiljJe that their ancestors may iiave 

 bet'n introduced without a direct land connection with any other part of the 

 wxald.' There does not appear to Ije of necessity any connection at all between 

 the line of rotlent and that of marsupial inunigration ; the fact that the rodents 

 have come down from the north does not appear to prove that tiie marsupials did, 

 any more than it proves that the fish Clalaxias is an innuigrant from Asia. 



Again Mr. Lydekker says,t after referring to the alliance between Dasyurida; 

 and the Ditlelphyida', "This Ijcing so, it is a, fairly safe assumption that l)otii 

 families are descended from a single connnon ancestral stock which, apart fiom 

 any (question of a connection Ijetween Australia and Soutii America, can hardly 

 have originated anywhere than in the northern heniispliere, seeing that the 

 Didi'lphyida' aie totally unknown in Notogwa," and then he makes the suggestion 

 that the Dasyurid;e and Didelphyidte were both differentiated in south-eastern 

 Asia, whence " lle^jresentatives of the former family soon afterwards found their 

 w;iy into Australia and New Guinea, while the oj)ossunis would appear to have 

 dispersed in one direction into Europe and in the other into North America, 

 eventually making their way tVoni the latter country at a late epoch in the 

 Tertiary period into South America." 



In respect to this it may be pointed out that there is as yet, as Mr. Lydekker 

 hiuLself says, no evidence of fossil Tertiary marsupials in Asia,, and further, that 

 even if the Dasyurithe and Dideliihyithe are supposed to have developed in that 

 region, the difficulty of accounting for the non-aj)pearance of the latter in the 

 Australian region is still at least as great as, if indeed not greater than, on the 

 sut)position that there was a. connection between 8outli America and Australia,. 



* Lw. cit., \\ 41. t Uic. fit., p. in 



