534 bulletin: museum of comparative zoology. 



Type. — A skin, collected July 26 or 27, 1822, by William Scoresby, 

 in Jameson's Land, east coast of Greenland, about lat. 71° N. Ac- 

 cording to Brown the specimen was in the Edinburgh Museum of 

 Science and Art, where he examined it in 1868. 



General characters. — Above, in summer, a mixture of blackish 

 and gray, with a wash of ochraceous over the fore shoulders, sides, 

 and belly; a black median stripe from nose to shoulders. Tooth- 

 pattern differs from that of other American species in the reduction 

 of the small postero-internal enamel-fold on the first and second 

 upper cheek-teeth to a mere point so that it is practically absent, 

 yet the posterior border of the last internal closed triangle is strongly 

 concave in each tooth. From the rubricatus group it differs in lack- 

 ing the small antero-external enamel-fold on the last lower molar, 

 though that on the inner side is present. 



Color. — Summer pelage: — dorsal surfaces, nose, and cheeks, a 

 general grizzled gray, due to the mixture of hairs having nearly the 

 middle third white, succeeded by a very narrow ochraceous ring and 

 a black tip. On the neck and shoulders, the ochraceous rings are 

 broader, and on the ears, sides, and at the root of the tail occupy the 

 entire tip of the individual hairs, excluding the black. The general 

 effect is of an ochraceous-orange wash at the shoulders, slightly redder 

 and more mixed with black dorsally. A narrow black median stripe 

 runs from the forehead to the shoulders. Upper surfaces of feet and 

 the tail silky white with a slight buffy tinge. Under surfaces washed 

 with ochraceous-orange; soles of fore feet and the wrists white. The 

 concealed bases of the hairs are slate color. 



Winter pelage: — pure white throughout, the bases of the hairs 

 slate color. 



Skidl. — Comp'ared with specimens of approximately the same age, 

 the skull is smaller than that of D. rubricatus from northern Alaska, 

 the zygomata are less roundly bowed, and the interparietal instead 

 of being nearly rectangular with a slight anterior median projection is 

 more distinctly pentagonal, with the short lateral boundaries reduced, 

 and the two anterior sides meeting at a considerable angle (Plate 1, 

 fig. 10). 



The teeth, like the skull, are weaker and narrower, and the minute 

 postero-internal fold of enamel of the two anterior upper cheek-teeth 

 is proportionately more reduced, until it is a mere point. In the few 

 specimens examined the small additional antero-external enamel fold 

 of the last lower molar (usually present in the rubricatus group) is 

 lacking. 



