136 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
EVOTOMYS RUTILUS, (Pall.) Coues. 
Mus rutilus, PaLias, Nov. Sp. Qvad. Glirium, 1778, 246, pl. xiv, B. 
Evotomys rutilus, CouES, Proc. Acad. Nat. Sci. Phila, 1874, 187. 
Arvicola gapperi, Dat, Alaska and its Resources, 1870, 577. 
Hasirat.—Circumpolar regions of both hemispheres. 
Descript1on.—This animal is less than the average size of Arvicole 
proper, about equaling Pitymys pinetorum in dimensions, and in color it is so 
conspicuously different from any other of North America that the somewhat 
extended notice we shall give it is for the purpose mainly of settling its rela- 
tionships to its own varieties, not of distinguishing it from other species. 
With one exception, it has an external form indistinguishable from that 
of Arvicole generally. This exception is in the ears, which are always visible 
above the fur, even when, as in winter and in northernmost specimens, the 
pelage is longest and thickest. The ears are of ordinary shape, but differ 
from those of some species of neighboring sections in being very closely 
pilous, like a squirrel’s, for instance, instead of rather loosely hirsute. The 
hairiness forms a slight even fringe around the margin, but below internally 
is almost wanting; the part that is covered by the general fur of the head 
being otherwise naked, so that the portion of the auricle that projects beyond 
the general pelage is the only part really furred. The antitragus is well 
developed; and just at its base there is a slender tuft of long hairs equaling, 
if they do not exceed, the whole ear in length. 
Possibly the snout is a trifle less blunt than in some other Arvicolines ; 
but the difference, if any, is not very obvious. The end of the muzzle is 
completely hairy, except the two little pads in which the nostrils open ; 
beneath these, the hairs of the cleft upper lip fall like a moustache over the 
teeth, completely hiding the edges of the lips. The eye is of ordinary size, 
and in the usual situation relative to snout and ears. The whiskers are medium 
in number and length, equaling—some of the longer ones a little exceeding— 
the head. The fore feet are from little less than half to about three-fifths 
the hinder. They are softly and densely hairy above and along the sides, 
only the palmar tubercles and under surfaces of the annulated fingers being 
completely exposed. The 3d and 4th digits are of about equal lengths and 
longest; the 2d is much shorter; the 5th a little less than the 2d; the 1st 
obsolete. The furriness of the feet is much the same as that of the hands; 
the soles being hidden to the tubercles, and the sides of the toes fringed with 
