184 Bulletin American Museum of Natural History. [Vol. XIX.] 



known Old World type; a shrew (Sorex buxtoni) much more 

 nearly related to certain Alaskan forms than to any other; 

 the Kamchatkan Bighorn (Ovis nivicola), which is so much 

 more nearly related to the American type of Ovis than to any 

 Asiatic species that it was formerly referred to it. The Kam- 

 chatkan- Siberian Evotomys wosnessenskii is also more nearly 

 related to some of the Alaskan members of the genus than 

 to any of its Old World congeners. Microtus, Arctomys, Vul- 

 pes, and apparently Ursus, afford nearly parallel cases. 



There is thus evidence that eastern Siberia has derived 

 some of its present mammalian life from boreal America, and 

 doubtless within a comparatively recent period. The Amer- 

 can origin of various early types that eventually attained 

 circumpolar distribution, as the horse, camel, and rhinoceros 

 phyla, etc., is now well established by palaeontological evi- 

 dence, but that the same is true of some forms of the existing 

 mammalian fauna does not appear to have been heretofore 

 recognized. 



