RODENTIA SCIURItfAK 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 mexicanus, AUD. & BACH. N. Am. Quad. Ill, 42 ; pi. cix, (figure of supposed young of S. mexicama, 



correctly marked S. spilosoma in. pi. cix of large edition.) 



SP. CH. Size less than Sciurus hudsonim ; ears very short, almost obsolete ; tail vertebra;, 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 vertebras 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 

 tbo black can be easily detected at all. 

 41 L 



