VOL. VIM, pp. 139-142 DECEMBER 28, 1893 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON. 



DESCRIPTION OF A NEW SPECIES OF ARVICOLA, OF 

 THE MYNOMES GROUP, FROM ALASKA. 



BY E. W. NELSON. 



Arvicola operarius sp. nov. 



THE TUNDRA MOUSE. 



ix Itomdis NeLson and True, Report upon Natural History 

 Collections in Alaska, 1887, pp. 275, 276, Series A (not Richardson). 



Type No. 2 1 III- United States National Museum. From St. Michaels, 

 Norton Sound, Alaska. November, 1879. Collected by E. W. Nelson. 



Measurements. Average measurements, in millimeters, of five 

 dried skins, fall and winter specimens, from St. Michaels are 

 as follows: Total length, 104.5; length of tail vertebrae, 25.2; 

 hind foot, 17.9 ; ear from front base, 9.8. 



Color. The dorsal surface, including the top and sides of the 

 head, is pale, dull fulvous or fawn color, thinly washed with 

 darker from the overlying black tips of the long hairs. On the 

 sides the fulvous of the back shades gradually into the paler 

 lower surface and sometimes forms a faint wash over most of the 

 under parts. The top of the tail is dark brown, in contrast with 

 the color of the back, and its sides and lower surface are white. 

 The under surface is plain, dull, grayish white, including upper 

 lips, chin, and throat, and extending laterally to the insertion 

 of the legs. In some cases the white area is separated from the 

 >yhite under surface of the tail by a narrow band of fulvous 



22 BIOL. Soc. WASH., VOL. VIII, 1893, (139) 



