Vol. VIII, pp. 139-142 December 28, 1893 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON./ 



- \- 



DESCRIPTION OF A NEW SPECIES OF ARVICOLA, OF 

 THE IMYNOMES GROUP, FROM ALASKA. 



BY E. W. NELSON. 



Arvicola operarius s[). iiov. 



THE TUNDRA MOUSE. 



Arricdid rij>ariiis hori'dUa Nelson and True, Repoi't ajton Natural History 

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



Type No. 2 2 21.5- United States National Museum. From St. Michaels, 

 N(jrton Sound, Alaska. Novemlter, 1879. Collected by p]. W. Nelson. 



Me ma roar. Ills. — Average ineasurenieuts, in niillinieters, of live 

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

 as follows: Total leng'th, 104.5; length of tail vertebrie, 25.2 ; 

 hind foot, 17.9; ear from front l)ase, 9.8.' 



(Jolor. — 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 )>lack tips of the long liairs. On the 

 sides the fulvous of the back shade-^ gradually into the paler 

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

 under parts. The top of tlie tail is dark l)rown, in contrast Avith 

 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 

 white under surface of the tail by a narrow baiid of fulvous 



•.i2-Bi0L. Soc. Wash,, Vol. VIII, WXi. (l:W) 



