Page:Natural History of the Ground Squirrels of California.djvu/56

642 shoulder patches, deep cinnamon-brown, the hairs individually being black, tipped with cinnamon; middle of back darker in tone than top of head; spot above upper eyelid blackish; cheeks and sides of neck much darker in tone than in beecheyi; whitish shoulder patches, restricted in extent, dull and indistinct as compared with fisheri and douglasii, even more so than in beeclieyi. Under surface of body very dark in tone, the hairs extensively grayish bister at bases and tipped with cinnamon buff. Tail and feet colored as in beecheyi.

Color variations.—The type and one other specimen show a black patch on the crown, due to lack of cinnamon hair-tippings; this, of course, is merely an individual feature.

The May-taken series at hand shows various transition stages from winter to summer pelage. In most of the specimens the fore parts are in fresh harsh summer coat, while the rump is still covered with the winter coat, showing underfur, and being more or less worn and faded. The tail in some examples is markedly worn and faded, with the usually resulting changes in color. In some specimens the hairs of the tail show but two dark bands instead of three; but this variation occurs also in other near-related races of ground squirrels. The two skins taken in February are in full winter pelage, showing more or less underfur over the whole body and no signs of molt. The fore parts, as compared with the summer pelage, are less bright in color tones, and the shoulder patches are even less distinctly whitish. Hinder upper surface and tail exactly as in beecheyi of same season.

Measurements.—Average and extreme measurements, in millimeters, of nineteen full-grown specimens from near Avalon, Catalina Island, are as follows: Seven males: total length, 471 (447–495); tail vertebræ, 189 (175–200); hind foot, 59 (55–63); greatest length of skull, 60.2 (56.1–63.7); zygomatic breadth, 36.9 (33.8–39.2); interorbital width, 14.8 (13.3–15.9). Twelve females: total length, 444 (406–475); tail vertebræ, 179 (161–194); hind foot, 56 (53–62); greatest length of skull, 57.7 (54.0–62.4); zygomatic breadth, 35.9 (33.3–37.6); interorbital width, 14.3 (13.0–15.4).

Close examination of the series of skulls shows to us no character by which to tell them from beecheyi or fisheri except for average greater size. There is the usual range of variation in proportions, due to age, this factor being judged from degree of wear on the crowns of the molariform teeth. Old skulls are largest, broadest relatively to length, and with most prominent ridges and processes. It is difficult for us to understand how Elliot (1904, p. 263) could have assigned the numerous cranial characters he did to the form he named, except on the ground that he examined but a very few specimens of beecheyi and fisheri and that these happened to be extreme.

Type locality.—Santa Catalina Island, California (Elliot, 1904, p. 263); more exactly, vicinity of Avalon, according to the collector of the type, Mr. John Rowley, in interview.

Distribution area.—Santa Catalina Island, California. Life-zone, Upper Sonoran.

Specimens examined.—A total of 21 skins and skulls, all from the vicinity of Avalon, Catalina Island. Two of these (including the type) were loaned us from the Field Museum of Natural History, Chicago; and nineteen were loaned us from the Museum of History, Science and Art, Los Angeles.

Only three species of rodents are known to be native to Catalina Island, a harvest mouse, a white-footed mouse, and the Catalina Island Ground Squirrel. This last-named animal is, as in each of the other cases, but slightly differentiated from its counterpart on the adjacent mainland. With little doubt it differs no more from its near relative, the Beechey Ground Squirrel, in general habits and traits, than it does in structure.

Until the present year very little has been known of the Catalina Island Ground Squirrel. In fact, the original characterization of the race was so unsatisfactory as to leave doubts in the minds of some students as to whether the island animals really differ at all from the