798 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
localities, as well as with the detailed descriptions given by authors of the 
Old World form. Examples from Fort Resolution, Fort Rae, Fort Liard. 
Fort Simpson, and Nelson’s and Mackenzie Rivers are much paler than 
those from the region more to the southward, with less rufous edging to the 
black stripes of the back (many of them being quite without such edging, 
just as in Siberian examples) and less rufous on the sides of the body. 
Specimens taken along the forty-ninth parallel are intermediate between 
those from the far north and the bright richly-colored phase commonly met 
with in the mountains of Colorado. Many of the specimens from the Black 
Hills of Montana are equally rich in color with those from Colorado, being, 
in most cases, absolutely indistinguishable. Others of like tint come from 
the Uintah and Sierra Nevada Mountains In the Coloradan or quadrivittatus 
form, the rufous of the sides assumes a peculiarly rich, lively tint of rust, the 
light dorsal stripes are whiter, and the dark ones are more intensely black 
and more narrowly edged with rufous. A much paler form is met with on 
the plains east of the Rocky Mountains, wherever the species is represented, 
becoming palest in the Mauvaises Terres region, where it also decreases very 
much in size. The form met with in the Rocky Mountain ranges north of 
the South Pass is larger, and has the rufous parts of a duller brown than is 
seen in the form which prevails in the mountains more to the southward. 
In the Bitter Root and Cascade ranges, the size still further increases, and 
the colors become still duller and heavier, passing here into the very large 
and peculiarly dark form of the coast region of Washington Territory and 
British Columbia. In this phase, the rufous tint of the sides no longer 
brightly contrasts with the general color of the dorsal. surface, which has 
become of a nearly uniform shade of dull yellowish-rusty-brown, varied with 
three or five (generally five) more or less strongly defined longitudinal stripes 
of black ; in many instances, the spaces between the stripes are not different in 
tint from the general color. In some cases, the general color is so dark that 
the outer black lines are effectually obscured, and the others are only dimly 
defined. In other examples, from the same region, the intervals between the 
dark lines are decidedly lighter than the general surface, varying in some 
specimens (especially the outer stripes) to grayish-white. The hairs of the 
tail become deep reddish-brown at the base, and tipped with white instead 
of yellowish-white. In passing southward, the size decreases, the general 
color lightens, especially on the sides, and the light and dark stripes become 
