SCIURIDM—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. beecheyji. 
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 
