118 Bailey The American Voles of the Genus Eroto)ni/s. 



Tail about 30 mm. long, thick, and densely 



bristly rutilus. 



Tail about 33 mm. long, not very thick or 



densely bristly dan'Kon i. 



Size small, hind foot 18-19 mm., dorsal stripe not 

 ferruginous. 

 Smallest of the genus, foot 18, dorsal stripe 



dark, rich chestnut in summer loringi. 



Slightly larger, foot 19, tail relatively shorter, 



dorsal stripe pale chestnut in summer . . . brevicaudas. 

 Dorsal stripe not sharply defined, blending with color 

 of sides. 



Tail indistinctly bicolor, dorsal stripe dull 



brownish wranglei. 



Tail distinctly bicolor, dorsal stripe plain 



chestnut rhoadsi. 



Ears gray or dusky, not distinctly rufous-tipped. 



Posterior edge of palate straight, colors bright, tail bicolor. 

 Dorsal stripe not sharply denned (dark chestnut in 



summer pelage) carol inensis. 



Dorsal stripe sharply defined (hazel or chestnut). 

 Sides clear, bright gray, skull long and narrow, 



hind foot 20 idahoensis. 



Sides dark buffy gray, skull wide and angular, 



hind foot 18 nivarius. 



Posterior edge of palate with a median projection, colors 

 dark in all but mazama. 

 Colors dusky or blackish above. 



Tail unicolor or nearly so, dusky or blackish, hind 



foot 18 , occidenlalis. 



Tail bicolor, blackish above, whitish below, hind 

 foot about 21. 

 Tail long, colors dark, skull thick and wide 



interorbitally californicus. 



Tail shorter, colors not so blackish, skull 



slender and narrower interorbitally olscnrus. 



Colors not dusky or blackish. 



Dorsal area dull hazel, sides grayish, skull broad, 

 angular, and flat-topped mazama. 



Evotomys rutilus (Pallas). 



Mus rutilus Pallas, Nov. Sp. Quad. Glirium, 246, pi. xiv B, 1778. 



Geographic distribution. Arctic regions of America, Europe, and Siberia. 



Type locality. Siberia, east of the Obi. 



General characters. Rather large and bright colored ; always recogniz 

 able by the short, thick, bristly tail and stout hind feet ; fur long and 

 soft ; feet and ears densely haired. 



