II.] MARSUPIALS IN ASIA. 57 



With regard to the presumed survival of marsupials in south- 

 eastern Asia till the Tertiary epoch, it may be mentioned that 

 although there is a total lack of knowledge of the early Tertiary 

 mammals of Asia, yet there are not wanting indications of an 

 affinity between the fauna of the eastern portion of the latter 

 continent and that of North America which points to a migration 

 from a common centre along the two sides of the Pacific; a 

 migration which in the early Tertiary period received on the 

 American side an abrupt check by the sea then dividing North 

 and South America. There is, for instance, living in Central Asia 

 a species of deer so closely allied to the North American wapiti, 

 that it is a question whether the two are really entitled to specific 

 distinction ; while the Chinese alligator has its nearest living ally 

 in the species inhabiting the Mississippi. Another piece of 

 evidence is furnished by the occurrence in the Tertiaries of the 

 Balkan Peninsula of remains of the perissodactyle genus Titano- 

 therium, belonging to a family only known elsewhere in North 

 America. Quite recently remains of the North American masto- 

 don {Mastodon americanus] have been discovered in eastern 

 Russia 1 . 



The existence of such essentially American types in Eastern 

 Europe and Central Asia clearly seems to point to a more intimate 

 connection between the faunas of those regions than exists 

 between those of Western Europe and North America; and thus 

 lends countenance to the idea that marsupials may have lingered 

 on in Eastern Asia till long after the earlier forms had disappeared 

 from Western Europe. On this view, it is quite probable that the 

 opossums of the Oligocene of Europe may have been immigrants 

 into that area from the south-east ; this being confirmed by the 

 absence of the group from the Ethiopian and Malagasy regions. 

 As already said, the existence of Australian types of Muridce 

 in the Philippines affords a pretty clear proof that Notogaea 

 received its fauna from south-eastern Asia, where types that had 

 died out elsewhere at an earlier epoch appear to have survived. 

 Doubtless, however, the Muridce effected their entrance into 

 Australia at a later epoch than the marsupials. 



1 See Pavlow, Mem. Ac. St Petersbourg, ser. 8, vol. i. pt. 3 (1894). 



