SCIURID.33— ARCTOMYS MONAX. 913 



proportions of the two colors greatly varying in different specimens, and prob- 

 ably in the same individual at different seasons. The long, coarser, overlying 

 hairs are colored basally like the under fur; the portion of the hairs project 

 ing beyond the under fur is thicker than the basal portion, generally intense 

 black, with the tips clear white, grayish-white, or yellowish-white. The mixed 

 color of the surface results from the fulvous zone being more or less visible 

 through the gray and black surface tints. The ventral surface is thinly 

 haired, and generally almost without under fur. The hairs are here two- 

 colored, being black basally, with the terminal half fulvous or rufous. The 

 tail-hairs are generally wholly black or brownish-black to the base, with gen- 

 erally gray tips, and sometimes an admixture of brownish. The anterior 

 half of the dorsal surface of the body is generally much grayer than the pos- 

 terior half, the gray sometimes forming a strongly marked gray shoulder- 

 mantle. In No. 1571, from Essex County, New York, the middle and posterior 

 part of the back is black, with the sides of the shoulders gray, presenting 

 nearly the pattern of coloration seen in Spermophilus grammurus var. beecheyi. 



In the large series of New England specimens before me are some almost 

 wholly black throughout, with the sides of the nose and chin gray and the long 

 hairs of the body slightly gray-tipped. Others are brownish-black and more 

 varied with gray; others still are strongly brownish-black posteriorly, and more 

 varied with gray anteriorly and on the sides. In some that present the usual 

 or more general phase of coloration, the top of the head is deep black ; in 

 others, brownish-black ; in others still, it is scarcely darker than the rest of 

 the dorsal surface. In some, the under fur is pale whitish-fulvous ; in others, 

 simply fulvous, varying in still others to rusty-yellow. In the latter, the sides 

 of the breast and the region surrounding the point of insertion of the fore 

 limbs are bright reddish-chestnut, and the whole lower surface is strongly 

 ferrugineous, with the hairs lighter-tipped over the middle of the belly. In 

 all the specimens, the feet are all either intense black or deep brownish-black. 

 In one specimen, from Nelson's River, H. B. T., the whole ventral surface is 

 bright reddish-chestnut. There is also a specimen in the collection from the 

 Hudson's Bay Territory wholly black. 



Young specimens, one-third to two-thirds grown, are usually much lighter 

 colored than the adults. In these, the under fur is either wholly gray, or gray 

 with a faint tinge of pale fulvous, and the white tips of the hairs are much 

 longer than in older specimens. The pelage is generally thinner, with a 



peculiar aspect of immaturity. 

 58 m 



