136 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 



EVOTOMYS RUTILUS, (Pall.) Coues. 



SftM nililim, Pallas, Nov. Sp. Qvatl. Gliriura, 1778, 24G, pi. xiv, 11. 

 Erotomya rutilus, Coues, Proc. Acail. Nat. Sci. Phila. 1874, 187. 

 Arvieola gapperi, Dall, Alaska and its Resources, 1870, 577. 



Habitat. — Circumpolar regions of both hemispheres. 



Description. — This animal is less than the average size of Arvieola 

 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 Arvieola 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 ringers 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 



