322 
U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
A specimen (No 141) differs from that just described (142) in being larger, and having the 
light spots very indistinct and scarcely appreciable, even posteriorly. It is probable that the 
spots are most distinct in younger specimens. 
The differences between this species and S. mexicanus can be readily expressed. The ears are 
decidedly shorter and more rudimentary ; the tail is narrower, much less busby, particularly 
on the basal portion ; the claws are larger and blacker, the thumb claw larger, the soles more 
hairy. The color is brighter, being strongly reddish brown or cinnamon ; the spots are not 
arranged serially, and are more indistinct, their posterior portion only, black instead of the ante¬ 
rior likewise, this being due to an essential difference in the colors of the hair occupying the 
spots. In S. mexicanus they are black beyond the lead-colored base, with a subterminal light 
portion and black tip ; in the present they are reddish brown beyond the basal color, then light- 
colored, and tipped only with black. The basal color, generally, is much deeper. The hairs 
on the sides of the extremity of the tail have one black central space, with a narrower base, and 
tip of lighter tints, while those at the extreme tip are black to the base, with light tips ; in S. 
mexicanus all these hairs have two black rings, both at sides and tip, the light portion being 
uniform throughout. 
It is true that the young animals are more distinctly spotted than the adults, but they may 
always be distinguished from small specimens of S. mexicanus by the fact that the spots are not 
arranged in regular linear series, and are not distinct on the anterior half of the body. The 
ground color is also always more chestnut in tint. 
Differences of equal value are discernible in the skulls; that of the present species being 
shorter, broader, the orbits larger, the muzzle blunter, &c. 
S. townsendii differs in having the ground color above darker, and a much shorter tail. 
This species was first described from specimens collected on the western coast of Mexico. The 
vicinity of El Paso seems to he its eastern, and the Gila its northern limit. It was erroneously 
considered to he the young of Spermophilus mexicanus by Audubon and Bachman. 
List of specimens. 
Catalogue number. 
Corresponding number 
of skull. 
Sex and age. 
Locality. 
When col¬ 
lected. 
Whence and how ob¬ 
tained. 
Original number. 
Nature of 
specimen. 
Measurements. 
Collected by— 
Tip of nose to 
tail. 
Tail to end of 
vert. 
Tail to end of 
hairs. 
Length of hind 
foot. 
290 
1651 
Chihuahua city. 
1853. 
John Potts. 
Skin. 
6.50 
1.10 
1059 
1855. 
7.00 
2.20 
3.00 
1.25 
1042 
2216 
Janos. Sonora ..i 
! April, 1855 
Maj. W. II. Emory __ 
Mounted .. 
5.75 
2.60 
3.20 
Dr. C. B. Kennerly. 
141 
1123 1 
o 
El Paso . 
1852. 
do. . 
6.50 
3.00 
3.75 
1.25 
T D ninrfc. .. 
142 
1124 2 
1852.... 
.. do.. .... 
..do.. ...... 
5.50 
2.50 
3.00 
1.25 
.do... 
2620 
Fort Thorn, N. M. 
Dr. T. 0. Henrv. 
1.15 
2619 
Fort Stanton, N. M. 
1.26 
1 
1 Skull 1.54-J- .98 inch; mamma 10. a Skull 1.45 -f. .97 inch. 
