526 bulletin: museum of comparative zoology. 



Color. — Adult in suvnner: — general tone of the upper surfaces a 

 ruddy gray, varying in intensity to a decided brownish. In detail, 

 the sides of the nose and flanks are buff-yellow, sides of the shoulders 

 and a band across the throat washed with clear tawny, ears tawny, 

 nose a mixture of blackish and buffy hairs forming a dark grizzled 

 patch which is continued as an ill-defined black median stripe to the 

 tail; cheeks and a patch below the ear buffy gray; rest of the upper 

 parts a uniform buffy to brownish gray due to a mixture of scattered 

 black hairs with others having a minute black tip and a broad sub- 

 terminal ring of ochraceous-buff shading into tawny in its upper half. 

 Base of tail like the body, its tip as well as the upper sides of the feet 

 whitish with a buffy wash. Beneath, the tips of the hairs are pale 

 cinnamon-buff varying to nearly clear cinnamon medially on the 

 chest in some specimens. 



Aduli in winter: — pure white throughout, the hairs plumbeous at 

 their bases. 



Immature and young are similar in summer coat to the adult, but 

 lack the ruddy tones. The black dorsal stripe is darker and more 

 clearly defined; the ear-patches are black. The upper surfaces, 

 cheeks, and sides are a mixture of black hairs with hairs having black 

 tips and broad subapical rings of ochraceous-buff, the latter color 

 nearly clear on the sides of the nose and fore shoulder. A collar of the 

 same encircles the throat; elsewhere the under surfaces are soiled 

 whitish with a buffy wash. Upper sides of feet dusky. Fur every- 

 where slaty at the base. 



In coloration, the adults of typical richardsoni show an approach 

 to the uniformity of hue in hudsonius, and quite lack the brilliant and 

 contrasting colors of Alaskan specimens of rubricatus. The more 

 yellowish tone, as compared with hudsonius, is obvious, however, and 

 is equally apparent in the young. Occasional adult specimens are 

 very ruddy, due to the strong development of the tawny-colored 

 bands on the individual hairs. 



Skull. — In the original description. Dr. Merriam drew attention 

 to the similarity in pattern between the molars of this and the Alaskan 

 Collared Lemming, but considered them smaller and narrower. He 

 further pointed out that the rostrum and nasals are proportionally 

 longer, and laid particular stress on the " broadly rounded and rather 

 depressed bullae." With a large series of both forms for comparison, 

 the last character does not appear as striking as originally claimed, 

 though the bullae average larger in richardsoni and are slightly more 



