-^Pq""!!!^] ALLEN — MAMMALS 49 



1914 



MAMMALS. 



By Glover M. Allen. 



The collection of small mammals obtained by Mr. Koren during 

 his Siberian trip and generously presented to the Museum of 

 Comparative Zoology by Mr. Thayer, proves to be of unusual 

 interest, and indicates that the Kolyma region, shut off as it is 

 by mountain ranges from the Kamtchatka and middle Siberian 

 country, is an area of faunal differentiation, where, rather unex- 

 pectedly, nearly all the smaller species seem to be represented by 

 distinct local forms. Mr. Bangs tells me that, with birds, the 

 Lena River is found to mark more or less nearly the eastern limit 

 for many species common to Europe and northern Asia. Eastward 

 of this river rises the Kolyma plateau, which is practically the cold 

 pole of the northern hemisphere. The rigorous conditions under 

 which the mammals live, is evidenced by their extraordinarily long 

 and thick winter coats. There seems to be a distinct tendency to a 

 shortening of the tail in some, as the shrews, compared with more 

 southern representatives of the same species, and in others the 

 entire body seems to be smaller in dimensions (for example, the 

 white lemming). 



Of particular interest, among the fourteen species obtained, are 

 two specimens of the genus Myopus, the known range of which is 

 thereby definitely extended from the Altai Mountains to the shores 

 of the Arctic Sea of East Siberia. A small species of Lemmus 

 appears to be the Old ^Yorld representative of L. minusculus of 

 Alaska. Four species of shrews appear to represent new local 

 races. One of them is closely allied to Sorex daphaenodon, a very 

 distinct type hitherto known from the island of Saghalien only. 

 Another shrew is clearly the representative of the S. araneus of 

 Europe, and with it occurs a smaller species, of a group previously 

 supposed to represent that animal, but which is probably nearer 

 some American species. The shrew representing S. araneus is 



