Page:Natural History of the Ground Squirrels of California.djvu/67

Rh , in millimeters, as follows: Male and female (nos. 117301 and 117300, respectively, Biol. Surv. coll., U. S. Nat. Mus.): Total length, 470, 465; tail vertebræ, 194, 205; hind foot, 58, 54; ear from crown, 20, 21; greatest length of skull, 61.2, 58.4; zygomatic breadth, 38.5, 37.0; interorbital width, 15.4, 14.2.

No skull differences of crucial importance between grammurus and beecheyi are apparent to us in the material at hand for study.

Type locality.—Purgatory River, near mouth of Chacuaco Creek, Las Animas County, Colorado (according to Cary, 1911, p. 87). This form was originally described by Thomas Say in 1823.

Distribution (in California).—Inhabits the Providence Mountains, in eastern San Bernardino County (see fig. 17); also "the canyons of the Colorado River" (Merriam, 1910, p. 2). Life-zone chiefly Upper Sonoran.

Specimens examined from California.—A total of five, all collected by Frank Stephens, June 1 to 3, 1902, in the Providence Mountains, 5,000 to 5,500 feet altitude. These were loaned us from the Biological Survey collection, United States National Museum.

The Rock Squirrel is really a very close relative of the Beechey Ground Squirrel and its habits are doubtless closely similar. It is a wide-ranging form through the southern Rocky Mountain region, stations of occurrence in southeastern California being merely far western outposts. Two of the specimens from the Providence Mountains are young less than half grown; these were taken on June 1, and indicate a breeding date at about the same time of year as for other ground squirrels in the upper Sonoran zone.

Other names.—Oregon Spermophile; Bull Dog; Prairie Dog, part; Gopher; Bobby; Sand Rat; Short-tail; Woodchuck; Belding Ground Squirrel, part; Picket-pin, part; Spermophilus oregonus; Citellus beldingi, part; Spermophilus richardsoni.

Field characters.—A medium sized, short-tailed ground squirrel, of stocky build, and of brownish gray coloration without special stripes or markings of any sort (see fig. 20a). Length of body alone about 8½ inches, with tail about 2½ inches more.

Description.—Adult in slightly worn spring pelage: Whole upper surface of a general drab tone of coloration, tinged with cream-buff along sides and with dull cinnamon on top of head and down middle of back. There is usually a faint pattern of fine dappling. Eyelids dull white; whiskers black; ears clothed with short hairs, like top of head in color. Upper surfaces of feet tinged with warm buff; palms naked; soles naked except for sparse hairing forward from heel nearly to tubercles; claws horn-color, dusky at bases. Tail full-haired, flattish, widest about one-fourth way back from end; color on upper surface mostly like back, except for showing through of the hazel bases of the hairs, and for black zone about end succeeded by a buffy white fringe; under surface of tail bright cinnamon rufous, with a broad band of black at end and continuing backwards a little ways along either side, and the whole margined narrowly with buffy white. Under surface of body dull cream-buff, paling on throat and inner sides of legs; much brownish lead-color of the hair-bases shows through on abdomen.

Color variations.—As wear proceeds toward an extreme the whole coat becomes grayer, and the cream-buff tints tend to disappear by fading. Males usually remain much less worn than females; otherwise we can see no differences in coloration between the sexes. The material we have shows evidence of but one molt each year,