THE QUADRUPEDS OF ARIZONA. 361 
Observers agree in according to it decidedly arboreal 
habits. It is both a rock and woods-loving species, and 
Mr. J. H. Clark, who found it abundant at the copper 
mines, says it seems to choose its abode mainly with refer- 
ence to a supply of food, making its burrow indifferently 
in loose soil, under rocks, or in hollow trees. 
The Round-tailed Spermophile (S. tereticauda Baird) 
is a little known species, first described from specimens 
taken at Fort Yuma, whose precise extent of range re- 
mains to be determined. I have not met with it, and 
believe that no information concerning its habits has been 
put on record. The chief peculiarity lies in its tail, which 
is disproportionately long for this genus, cylindrical in 
Shape, and very long-haired. It is among the smaller 
Species, being only about six inches in length of body; 
is above of a light yellowish-brown, finely grizzled, and 
` below of a soiled yellowish-white. 
In addition to the preceding, several Mexican species 
may very likely extend into the Territory from Sonora. 
Such are S. Mexicana, 9. spilosoma, and possibly S. Cou- 
chii. The common little S. tridecemlineatus, of the Mis- 
Souri region, has been found so far south-west as Fort 
Thorn, N. M., and possibly should also be included. 8. 
lateralis, a species closely allied to S. Harrisii has been 
found in the Des Chutes Basin, and may extend as far 
south as Arizona. 
A step further from the true squirrels brings us to the 
Prairie “Dogs,” as they are called; formerly classed with 
the Spermophiles, to which they are closely allied, but 
now more properly placed in a distinct genus ( Cynomys). 
They mainly differ from the true Spermophiles in the ex- 
treme brevity of the tail, the very rudimentary cheek- 
pouches, and some dental and cranial peculiarities. The 
` AMERICAN NAT., VOL. I. 46 
