RODENTIA SCIURINAE SPERMOPHILUS. 305 



ca te very short, sometimes almost marginiform. Soles naked or hairy from behind the base 

 of the toes to the heel, or hairy only at the heel. 



The sub-genus, as thus characterized, is divided by Brandt as follows : 



Division A. Soles in the adult entirely naked, with stiffish hairs on the sides of the heel only, 

 margined and partly concealed by these incumbent hairs. Ears submarginiform truncate. 

 Tail moderate or short, about equal to the hind foot. 



Species. S.fulvus, rufescens, erythrogenys, brevicauda, mugosaricus, musicus. 



No species of this type are found in America. 



Division B. Soles in the adult more or less largely pilose. Ears very short, but much wider 

 than in the preceding section. Tail elongated, two or three times longer than the hind foot, 

 and, with the hair, about half the length of the body. 



The species of this division, as already stated, are S. parry i and S. eversmannii. 



Division C. Soles in the adult hairy, both behind the toes and on the heel. Ears short, but 

 distinctly margined. Tail moderate or sub-moderate, one-fourth to one-third the length of the 

 body. 



The species are S. guttatus, S. citillus, and probably S. townsendii. 



In reference to the pilose condition of the soles, Brandt remarks, that it is necessary to have 

 adult specimens, as the soles may be distinctly hairy in the young and perfectly smooth in 

 adults of the same species. 



2. OTOSPERMOPHILUS, Brandt. The first upper molar about one-third less than the second ; 

 conical acuminate, behind truncated a little obliquely and indented by a slight fossa. Crowns 

 of the second, third, and fourth molars nearly rhomboidal, slightly narrowed on the inner face, 

 sub-semilunar, and rounded. Triturating surface with the central ridges slightly elevated, 

 sub-parallel, unequal in length, anterior one longest, posterior indented in the inner limb. 

 Ears moderate or sub-moderate, about one-third the length of the head. Tail elongated. Soles 

 pilose behind the toes. This section is entirely American. 



In regard to the pilose condition of the soles, I find that the variation in the same species is 

 not as much with age as mentioned by Brandt, as with season, and that any characters based 

 on this feature are likely to bo very uncertain. Throughout the eared spermophiles, the sole 

 is almost invariably naked from the heel in summer, and coated with hairs nearly to the bases 

 of the toes in winter. A few species of the other American species have a small tuft of hair 

 on the soles the year round, but the amount of this varies with the season in all. The same 

 thing takes place in all the North American squirrels. 



The following synopsis may serve to facilitate the determination of the North American 

 spermophiles : 



A. OTOSPERMOPHILUS, Brandt. 



Ears prominent, as much so as in many squirrels or Tamias. Tail squirrel-like, half as long 

 as the body, or longer ; sometimes quite full and bushy. Thumb armed with a flat nail only, 

 not a claw. Soles naked in summer ; densely covered with short, close, velvety hairs in winter. 



1st. Tail (including the hairs) more than half the length of the body (about two-thirds). 



1. Body finely mottled above. A broad hoary white patch on the sides of 

 neck and shoulders, the upper edge extending back in a narrow line for 

 a short distance on the sides. Interval between these patches mottled 



like the hinder part of the back beecheyi. 



39 L 



