50 BIRDS AND MAMMALS OF EAST SIBERIA [ ' VqI.' V " 



further interesting in being a link between that species and S. 

 tundrensis of northern Alaska, which is clearl}^ its New World 

 representative. 



In his paper on mammals from eastern Siberia, in 1903, Dr. J. A. 

 Allen ^ pointed out this interchange of species between the two 

 continents, as exemplified in such species as Sorex buxtoni and 

 Evotomys wosnessenskii, whose affinities appear to be American 

 rather than Siberian. The large lemming described by Dr. J. A. 

 Allen as L. ohensis chrysogaster seems to be nearer the Alaskan 

 race of L. hudsonius. As stated by Dr. Allen, it is apparent that 

 land communication at some former geological time or times en- 

 abled such genera as Cervus, Alee, Ovis, Sorex, Evotomys, Micro- 

 tus, Lemmus, Sciuropterus, Citellus, Arctomys, Lepus, Ochotona, 

 and others to attain a holarctic distribution. It would seem, 

 further, that this distribution must have become interrupted for a 

 long period, so as to enable distinct forms to develop even on both 

 sides of the present Bering Strait. Later connections between 

 these land masses must be invoked to explain the interchange of 

 the above-noted closely related species of comparatively small 

 range in the respective continents. In the case of the shrews, 

 for example, the widespread S. richardsoni of northern America 

 may represent S. araneus of the Old World, but its advent here 

 is unquestionably earlier than that of the still more closely allied 

 S. tundrensis which merely has gained a recent foothold in the New 

 World. 



In addition to the species collected, Mr. Koren makes note of 

 the following mammals, of whose presence he found evidence. 



Foxes of the red-fox type, common. 



Arctic fox, common in lower Kolyma. 



Gray wolf, common. 



Lynx, said to occur in the upper Kolyma highlands. 



Brown bear, said to be common. 



Wolverene, common. 



Otter, not very common. 



Sable, said to occur in the upper Kolyma valley. 



I J. A. AUeu, Bull. Amer. Mus. Nat. Hist., 1903, 19, p. 183. 



