IX.] EASTERN DIVISION. 319 



tive species which characterise the two divisions of the present 

 one. It must, moreover, be remembered that in the case of the 

 other regions we have taken the whole of the peculiar generic 

 types into consideration, although many of them are confined to 

 small portions of such regions, whereas in the present instance 

 only those which range over nearly the whole area have been 

 mentioned. If, for instance, we were to take the genera respec- 

 tively confined to the Indian and Malayan areas of the Oriental 

 region, it would be found that the distinction between the two 

 areas would be nearly or quite as marked as are the two great 

 divisions of the Holarctic, while in the matter of species the 

 differences between the two would be far greater. There would 

 accordingly be stronger grounds for making an Indian and a 

 Malayan region than there are for the separation of a Palsearctic 

 and a Nearctic. 



Having now discussed the leading mammalian types character- 

 istic of the Holarctic region as a whole, it remains 



to notice those confined to its eastern division, t f 



after which such as are restricted to its western half Holarctic 

 will be taken into consideration. And here it is 

 advisable to repeat that since the communication between eastern 

 Asia and North America by way of Bering Strait appears always 

 to have been of very limited extent, as we proceed south in the 

 two great continental areas the difference between their faunas 

 appears more and more strongly marked. Accordingly, if it were 

 possible definitely to establish a Mediterranean region, the dis- 

 tinction between the faunas of the eastern and western divisions 

 of the Holarctic would be much less than is the case under the 

 arrangement here followed. 



Passing by the bats entirely, no notice will be taken of groups 

 which, like the hedgehogs (Erinaceus), are spread over several of 

 the regions of Eastern Arctogaea, since these are not in any way 

 characteristic of the eastern division of the Holarctic region 1 . 

 The first mammal that presents itself for notice is accordingly the 

 water-shrew, which is the sole representative of the genus Crosso- 

 pus, and belongs to that division of the Soricidce in which the 



1 Such types have been discussed when considering the fauna of Eastern 

 Arctogaea, supra, p. 181. 



