THE GROUND SQUIRRELS OF CALIFORNIA. 



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urements, in millimeters, as follows: Male and female (nos. 117301 and 117300, 

 respectively, Biol. Surv. coll., U. S. Nat. Mus.) : Total length, 470, 465; tail vertebrae, 

 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 ciucial 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 alti- 

 tude. These were loaned us from the Biological Survey collection, United States 

 National Museum. 



The Eock 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, sta- 

 tions 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. 



OREGON GROUND SQUIRREL. 

 Citellus oregonus (Merriam). 



PLATE II. 



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 oeldingi, 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 8$ inches, with tail about 2$ 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 eee no differences in coloration 

 between the sexes. The material we have shows evidence of but one molt each year, 



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