RODENTIA SCIURINAE TAMIA8. 291 



TAMIAS, Illiger. 



Tamias ILLIGKR, Prod. Syst. Mara, et Av. 1811, 83. 



AUD. & BACH. N. Am. Quad. I, 1849, 64. 

 Tenotis, RAFINESQUB, Am. Month. Mag. I, 1817, 362. 



Cheek pouches ample, extending to the occiptit. Tail shorter than the body, not bushy. The species with three to five 

 dark dorsal stripes. Permanent upper molars four. The anterior basal plate of the zygoma perforated by a nearly circular 

 foramen. 



The genus Tamias bears somewhat the same relation to the squirrels that Spermophilus or 

 rather Otospermophilus does to Arctomys. It is composed of a very limited number of species, 

 two of which occur in Europe and Asia and the remaining four or five in North America. All 

 are marked with a median dark dorsal stripe, usually with two others on each side ; the 

 intervals between the stripes either of the ground color or lighter. 



The cheek pouches are ample in Tamias, and are capable of great distension, so as to hold a 

 large supply of food. They open anterior to or alongside the molars, and reach back almost to 

 the shoulder. 



The tail is short, less than the body, and the hairs, though longest on the sides, are com 

 paratively short; nor is the tail at all bushy. The feet are large, and the claws well developed, 

 in accordance with the fossorial habits of the species. 



The skull is depressed and narrow and tapers anteriorly to the end of the considerably 

 elongated muzzle. The dorsal outline is quite convex. The post orbital processes are slender 

 and styliform. The zygomatic arch is very gently and uniformly curved in itg inferior outline 

 from the temporal bone to where it melts into the intermaxillary on the upper part of the 

 . snout, instead of having a distinct angular bend upwards just opposite the inferior edge of the 

 zygomatic process of the maxillary. In this character it differs from all other Sciurinae. The 

 plane of the zygomatic plate of the maxillary, too, is more oblique to the vertical plane of the 

 axis, and there is a very distinct, nearly circular, foramen perforating the base of this plate, a 

 character entirely peculiar to Tamias among the squirrels. The tubercle below the foramen is 

 quite distinct. The permanent molars are only four in number and are quite small. They 

 are quite peculiar in having the plane of the grinding surfaces horizontal anteriorly, then 

 twisting gradually outwards, rendering the crown of the last molar quite oblique. The level 

 of the crown of the last molar, too, is considerably higher than that of the first, the external 

 outline of the alveoli rising behind in a similar manner, so that if produced it would intersect 

 the parietal bone considerably in advance of the occiput. Both outlines of the molar series are 

 gently convex, the anterior molars themselves a little wider apart than the posterior. 



The lower molars correspond with the upper ones in the twisting of the plane of the grinding 

 surface and its gradual elevation posteriorly. The lower jaw is much slenderer than in the 

 true squirrels ; the coronoid process is narrow, elevated, and much curved. The upper 

 incisors are compressed laterally ; as in Sdurus the lower have the antero-posterior dimensions 

 much less in proportion. 



The skull of Tamias exhibits a considerable resemblance in shape to that of the Tamias-like 

 Sphermophiles. It is, however, much more depressed. The anteorbital foramen is in the 



