RODENTIA'—SCIURINAE-SPERMOPHILUS SPILOSOMA. 
321 
SPERMOPHILUS SPILOSOMA, Bennett. 
Sonora Ground Squirrel. 
Spermophilus spilosoma, Bennett, Pr. Zool. Soc. I, 1833, 40. 
Wagner, Suppl. Schreb. Ill, 1843, 251. (Note.) 
Baird, Pr. A. N. Sc. Phila. VII, 1855, 332. 
Spermophilus rnexieanus, Aud. & Bach. N. A.m. Quad. Ill, 42 ; pi. cix, (figure of supposed young of S. mexicanus , 
correctly marked S. spilosoma in pi. cix of large edition.) 
Sp. Ch. —Size less than Sciurus hudsonius ; ears very short, almost obsolete; tail vertebral, about half the length of the 
body, or rather less, its hairs depressed and moderate in length ; thumb claw distinct, a central linear hairy patch on the 
sole, extending nearly to the end of metatarsals ; above reddish brown, with indistinct subquadrate spots of reddish white, 
most distinct posteriorly and in young specimens, with the posterior border only blackish, the hairs having black at the tip 
alone; tail margined and tipped with very pale yellowish brown, within which is a broad black border, the hairs on the 
sides of the tail having one median black bar, at the tip of the tail this black extending to the very base ; length, about 
7 inches ; tail, with hairs, a little more than half as much ; hind foot, 1.25 inch. 
This species bears a considerable resemblance in several points to S. mexicanus, so much so, 
indeed, that Audubon and Bachman have combined them as one. A comparison of many spe¬ 
cimens shows conclusively, however, that they are really more distinct than the latter is from 
S. 13 -lineatus. Its affinities are quite near to S. townsendii. 
The muzzle of this species is remarkably short, more so than in almost any species known to 
me, this character being evident in the skin as well as in the skull. The external ear is exceed¬ 
ingly short, appearing as if cut off very close to the skin, with the slightest possible projection 
above it. The thumb is armed with a short gouge-shaped claw which, though short, is as 
large as the basal half of that on the fifth finger. The nails generally are longer than in S. 
mexicanus; the third longest, the fifth extending beyond the base of that of the second. The 
palms are naked. The three central toes are nearly of equal length, the fifth reaching the base 
of the claw of the fourth, the first about to that of the fifth. The soles are covered with long 
hair down the middle, more densely than in S. mexicanus. The vertebree of the tail of this 
species are about half the length of the body, extending for about one-fourth their total length 
beyond the outstretched hind feet. The tail is rather thinly clothed with hair all over, almost 
cylindrical, with the hairs arranged longitudinally for the basal half, beyond which it widens 
out, with the hairs longer though much less bushy and flattened than in S. mexicanus. 
The ground color of the upper parts generally is a light reddish brown or cinnamon, varied, 
especially posteriorly, with numerous indistinct subquadrate spots of reddish white, about one- 
eighth of an inch in diameter, arranged irregularly as far as can be ascertained, and not serially 
as in S. mexicanus. These spots are bordered posteriorly by black, and there are other black 
hairs interspersed. The hairs are almost sooty black at the base, then reddish brown to the tip, 
except in those occupying the region of the light spots, where they are subterminally lighter, 
with the extreme tip black. The top and sides of the head, with the basal half of the upper 
part of the tail, are finely grizzled with the three colors just mentioned. The eyelids and under 
parts generally are brownish or reddish white. The longer lateral hairs on the terminal half 
or third of the tail are black for rather more than their central third, with the basal portion of 
the reddish brown described, and the apical light yellowish brown lighter than the base. At 
the extreme tip, however, the black extends to the very base, thus affording but the two colors. 
At no point can two rings of black be distinguished—it is only towards the end of the tail that 
t^c black can be easily detected at all. 
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