boundary of Modoc County. (See map, fig. 17.) Life-zone, Upper Sonoran and Transition, ranging down into Lower Sonoran along the western side of the Sacramento Valley. Altitudinally, the species ranges from near sea level up to as high as 6,500 feet (near South Yolla Bolly Mountain) and even 6,800 feet (on the Scott Mountains, Siskiyou County).
More in detail: The southern limit of the range of douglasii is not known to reach the Golden Gate; it falls, on the sea-coast, somewhere not far to the north of Point Reyes Station, and extends from there to the vicinity of Petaluma, leaving the southern two-thirds of Marin County uninhabited. It extends nearly or quite to Benicia and to the southern end of the range of hills west of Vacaville. The flood-plain of the Sacramento River forms the eastern boundary north to beyond the Marysville Buttes. Thence northeastward, across the Sacramento Valley, there is no obvious barrier. In Butte, Plumas and Lassen Counties the ranges of douglasii and beecheyi approach very closely, but so far as known they do not overlap; nor have undoubted hybrids or geographic intergrades been reported.
Specimens examined.—A total of 65, from the following localities in California: Modoc County: Sugar Hill, 3; Parker Creek, Warner Mts., 3; Deep Creek, Warner Mts., 1. Siskiyou County: Mayten, 1; six miles northwest of Callahan, Scott River Valley, 6; Summerville, 1; Castle Lake, 3. Shasta County: McCloud River, near Baird, 7. Tehama County: Mill Creek, 2 miles northeast of Tehama, 4; four miles south of South Yolla Bolly Mountain, 1. Butte County: four miles southeast of Chico, 4; Dry Creek, on Oroville-Chico road, 3. Glenn County: Winslow, 4. Yolo County: Rumsey, 1. Solano County: three miles west of Vacaville, 2. Humboldt County: Eureka, 1; Fair Oaks, 2; Ferndale, 1; Cuddeback, 1. Trinity County: Hayfork, 2; Helena, 2. Mendocino County: Sherwood, 3; three miles south of Covelo, 1; six miles north of Willets, 1; Mount Sanhedrin, 3. Sonoma County: seven miles west of Cazadero, 4.
The Douglas Ground Squirrel belongs to the group of large, bushy-tailed, tall-eared ground squirrels which include the California, Fisher, Catalina Island and Rock Squirrels, and in common with the first and second of these at least it is often called Digger Squirrel. Although the differences are not great, they are evident and should be recognized in economic work, for they not only concern color, but apparently also habitat and food preferences. The Douglas Squirrel differs from its next neighbor of the "digger" category, the California, in having a conspicuous blackish wedge-shaped patch on the middle of the back between the shoulders, in having the shoulder region more extensively grayish white, and in having the tail a little longer and grayer.
The name of the squirrel now under discussion was bestowed upon it (Richardson, 1829, p. 172) in acknowledgment to an early English explorer in western America, David Douglas, for having brought home specimens of the animals met with, many of which proved to be new to science. Douglas's travels carried him through parts of Oregon and probably northern California; but the type of this ground squirrel was a hunter's skin received from the Columbia River. There is no telling now exactly where it really came from originally, though probably from much south of the Columbia, since the species is not known to have existed within history that far north.
In northern California the Douglas Ground Squirrel occupies a wide area; in fact, at the extreme north from the Pacific Ocean to the Nevada line. To the southward its range includes all of the upper Sacramento Valley, and its western half lower down, and the whole coast region (hills and included valleys) south nearly to San Francisco Bay. Reference to the map (fig. 17) will show that the range of the Douglas is almost exactly complementary to that of the Beechey; at no point do
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