SCIURIDA—ARCTOMYS FLAVIVENTER. 921 
ARCTOMYS FLAVIVENTER Aud. and Bach. 
Rocky Mountain Marmot. 
Arclomys flaviventer AUDUBON & BACHMAN, Proc. Acad. Nat. Sci. Phila. 1841, 99; Journ. Acad. Nat. Sci. 
Phila. viii, 1842, 309; Quad. N. Am. iii, 1853, 160, pl. cxxxiv.—WaGnrr, Wiegmann’s Archiv. 
li, 1843, 45.—Scuinz, Syn. Mam. ii, 1845, 63.—Barrp, Mam. N. Am. 1857, 343, pl. xlvii, fig. 1 
(skull).—Suck ry, Nat. Hist. Wash. Terr. pt. iii, 1859, 99, 124.—I1aypxEn, Trans. Am. Phil. 
Soe. Phila. xii, 1863, 146.—Merriam, U.S. Geol. Sury. of Terr. 6th Aun. Rep. 1872 (1873), 664.— 
ALLEN, Proc. Bost. Soc. Nat. Hist. xvi, 1874, 294; Bull. Essex Inst. vi, 57, 66—Cours & 
Yarrow, Wheeler’s Expl. and Sury. W. of 100th Merid. v, Zo6l. 1875, 123.—GRINNELL, Lud- 
low’s Black Hills of Dakota, 1875, 82. 
Speciric cHars.—Length to base of tail about 17.09 to 18.50; of tail 
to end of vertebre 6.50 to 7.25; of tail to end of hairs 9.00 to 10.00. 
Above mixed gray, fulvous, and reddish-brown; below yellowish or golden, 
varying to rufous. The general color also varies to wholly black or brown- 
ish-black, as in A. monax. Sides of the nose and chin whitish-gray; top of 
the head dark reddish-brown; tail with the hairs at base pale reddish-brown 
to black, broadly tipped with yellowish-brown or rufous; feet yellowish- 
rufous, strongly varied with black. Ears rather small, thinly haired, yellow- 
ish-brown, sometimes edged with darker. Tail long, round, full, and bushy, 
with the hairs fully one-half to more than one-half the length of the head 
and body. 
The specimens before me chance to be quite uniform in coloration, but 
melanistic specimens are of frequent occurrence. A specimen from Fort 
Massachusetts, N. Mex., is everywhere dark brownish-black, slightly varied 
with gray. At Montgomery, Colo., where this species occurs in great abun- 
dance, and where I have seen a dozen or more sitting on the rocks at one 
time within easy rifle range, generally several black ones were to be seen 
associated with the others, as well as others more or less blackish. Usually 
the abundant under fur of the dorsal surface is dusky at base, then clear 
pale fulvous, passing into golden at the extremity. The overlying longer hairs 
are conspicuously white-tipped, with a broad subterminal bar of reddish- 
brown. The under surface is very thinly haired, with no under fur. The 
hairs are here dark reddish-brown at base, broadly tipped with fulvous, the 
tint varying in different specimens from pale yellowish to bright rufous. The 
tail is usually faded yellowish-brown at the surface, the hairs deepening into 
dark reddish-brown or blackish basally. The rump is generally clear yellow- 
ish, varied with the whitish-yellow tips of the longer hairs, and hence lighter 
