﻿SYNOPSIS OF THE AMERICAN SHREWS OF THE GENUS SOREX. 



By C. Hart Merriam. 



The object of the present i^aper is to furnish descriptions, on a com- 

 mon plan, of the principal types of American Shrews. Hence the mul- 

 tiplication of closely related forms has been avoided, and several fairly 

 well marked subspecies have been allowed to go unnamed. Forty-one 

 species and subspecies are here recognized, of which number 33 belong 

 to the restricted genus Sorcx, 1 to the subgenus MicTosorex^ 4 to the 

 subgenus Neosorex, and 3 to the subgenus Atopliyrax. The subgenera 

 are restricted to the northern United States and Canada, while 8orex 

 proper ranges from the Arctic Circle to Guatemala. The genus as a 

 whole is clearly of boreal origin, and, excepting the austral Sorex longi- 

 rostris and its relative S. fisher i., all of the southern forms are confined 

 to high mountains. 



The collection of mammals made by the Division of Ornithology and 

 Mammalogy of the Department of Agriculture contains about 1,200 

 specimens of long-tailed Shrews (genus Sorex). In stud ying this mate 

 terial and map[)ing the geographic distribution of the various species, 

 20 new forms were discovered and are here described. Four of these 

 are from Alaska, 1 from British Columbia, 4 from Mexico, and 11 from 

 the United States. 



All American Shrews have two pelages, which may be roughly desig- 

 nated as summer and winter coats, though by no means corresfjonding 

 strictly with these seasonal limitations. As usual among small mam- 

 mals, the molt takes i^lace at different dates among individuals of the 

 same species, so that it is not rare to capture specimens in different 

 pelages on the same day. The winter pelage is usually plumbeous, 

 dusky, or ash gray; the summer pelage sepia brown or chestnut. In 

 some species, as Sorex troivhridgii, the change of color is slight and 

 unimportant; in others, as S. vagrans and 8. personatus^ the difference 

 is striking. 



In defining the various species, cranial characters have proved serv 

 iceable and dental characters indispensable. The most useful cranial 

 characters are the size and form of the bram case, breadth of the 

 palate, length and degree of attenuation of the rostrum, and in some 

 cases the breadth of the iuterorbital constriction. The most important 

 dental characters are the size and depth of emargination of the molari- 

 form teeth and the proportions of the unicuspidate teeth. 



In studying the skulls and teeth of Shrews it is absolutely essential 

 to take into account changes due to age and wear. Old and young 

 skulls of the same species from the same locality differ surprisingly in 

 size, form, and massiveness. With increasing age the cranium as a 



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