Page:Natural History of the Ground Squirrels of California.djvu/96

676 claws blackish-brown, horn-color at tips; soles of hind feet naked nearly to heel. Chin and throat and insides of forelegs and thighs buffy white; belly with hairs extensively slaty brown at base, tipped with whitish; in other words, whitish with much slaty brown showing through. Tail well-haired, flat in form, broadest in middle portion, tapering somewhat toward end; in color, as viewed from above, chiefly black, with a margin of ochraceous-buff; there is considerable mixture with cinnamon-brown toward base, however, and separation of the hairs discloses the deeper-lying hazel color of their roots; lower surface of tail centrally solid hazel, paling to ochraceous-tawny at base of tail, then a zone of black, and then an outer fringe of bright ochraceous-buff. The body side-stripes are sharply defined along their edges, but at their ends fade out gradually; also the reddish of head blends by degrees with colors of body adjacent.

Color variations.—As far as we can see there is no difference in coloration between male and female, in spite of the extraordinarily bright pattern of coloration in this species. The young, even third-grown ones, are very similar to the adults in pattern, the difference consisting only in paler tones of color, especially about the head. There is, however, considerable change in the depth of coloration with season. In the spring and early summer the head region is much paler than in late summer and fall, and there is much other evidence of fading and wear to which the pelage has been subjected. In June specimens the head is pale cinnamon-buff.

As far as we can determine from the collection of specimens studied there is but one thorough-going molt each year and this takes place in June and July. The process is gradual. The exchange of old hair for new begins first on the head and progresses backwards; but specimens often show a patchy coat, with areas of dense new hair on the head or back surrounded by old worn hair.

We are unable to make out a distinguishable race from the Trinity Mountain region, trinitatis of Merriam, 1901, p. 126, type from "Trinity Mountains east of Hoopa Valley, California (altitude 5,700 feet)." The characters assigned, of color and size, are not borne out in our large series of specimens from the Trinity region as compared with series from the northern Sierra Nevada. There is, however, a slight tendency towards paling of colors in chrysodeirus at the southern end of the Sierra Nevada and along their east flank; for example, as shown by specimens from the east declivity of Kearsarge Pass, west of Independence. This modification is evidently in the direction of perpallidus.

Measurements.—Average and extreme measurements, in millimeters, of twenty full-grown specimens from the west slope of the high central Sierra Nevada are as follows: Ten males: total length, 272 (253–290); tail vertebræ, 89 (75–104); hind foot, 41 (38–43); ear from crown, 15.7 (11.0–19.0); greatest length of skull, 44.0 (42.2–46.2); zygomatic breadth, 26.6 (25.2–28.2); interorbital width, 10.4 (9.5–11.1). Ten females: total length, 266 (243–285); tail vertebræ, 83 (67–100); hind foot, 41 (39–44); ear from crown, 16.1 (13.0–21.0); greatest length of skull, 42.7 (41.0–44.1); zygomatic breadth, 25.9 (25.0–27.1); interorbital width, 10.3 (9.2–11.0).

It would appear from the above figures that in males the tail averages a little longer than in females. The skulls of old individuals, particularly males, relative age being estimated by degree of wear on the crowns of the molar teeth, show greatest size, particularly as regards zygomatic breadth and heaviness of rostrum. Old skulls also show wider brain-case, broader jugals, and stouter postorbital processes.

Weights.—Average and extreme weights, in grams, of twenty full-grown specimens from the west slope of the high central Sierra Nevada are as follows: Ten males, 181 (155–218); ten females, 199 (136–245). Averages, in ounces: males, about 6½; females, about 7.

The heaviest example (245 grams) was a pregnant female. Males average heavier in the fall, when they are fat, than in early summer.

Type locality.—Fort Klamath [mountains near], Klamath County, Oregon (Merriam, 1890, p. 10).

Distribution area.—Upper coniferous belt (Canadian and Hudsonian life-zones, less commonly down into Transition) along the Sierra Nevada, south as far as Cannell Meadows, in extreme southern Tulare County; north through the Mount Lassen country to Mount Shasta, and thence west through the Trinity, Scott and Salmon Mountains (Mus. Vert. Zool.) to extreme eastern Humboldt County (Merriam, 1901, p. 126); also on the Siskiyou Mountains, along the Oregon border of western Siskiyou County (Merriam, 1901, p. 126); on the mountain mass to the