. Monographs of North American rodentia [microform]. Rodentia; Paleontology; Rongeurs; Paléontologie. lii m\\' I ! ya\i. n 780 MOXOGRAPH8 OF NORTH AMERICAN RODBNTIA. in Sciurus; pelage generally full and soft; dorsal surface generally with two (sometimes four) longitudinal wiiitish stripes, bordered on each side with a stripe of black, and with (except in one species) a central dorsal stripe of black. As already stated {anted., p. 63f»), Tamias l)ears a strong resemblance to ?,r;M!e of the smaller species of Spermophilus, the two groups being in fact not sharply separable. The more important d
. Monographs of North American rodentia [microform]. Rodentia; Paleontology; Rongeurs; Paléontologie. lii m\\' I ! ya\i. n 780 MOXOGRAPH8 OF NORTH AMERICAN RODBNTIA. in Sciurus; pelage generally full and soft; dorsal surface generally with two (sometimes four) longitudinal wiiitish stripes, bordered on each side with a stripe of black, and with (except in one species) a central dorsal stripe of black. As already stated {anted., p. 63f»), Tamias l)ears a strong resemblance to ?,r;M!e of the smaller species of Spermophilus, the two groups being in fact not sharply separable. The more important differences are the following: — In Tamias, there is sometimes but a single upper premolar, and when two are present the first is very minute, scarcely larger than in Sciurus hudsonius; in Spennophilas, two are always present, and the first is functionally devel- oped, being from one-fourth to one-half the size of the second. In TamioK, the whole dentition is weaker and the teeth relatively smaller; the ante- orbital foramen is oval (sometimes quite narrow), and the outer and lower border is not generally developed into a projecting bony rim, culminating in a tubercle, as in Spermophilus. The notch in the posterior border of the zygo- matic maxillary process is situated more anteriorly than in Spermophilus. The skull is much more delicate and papery than in Spermophili of corre- sponding size, and showd no traces of the muscular ridges often seen in old skulls in the genus Spermophilus. The tail is usually also more flattened, and the general form of the animal is more Sciurine. Tamias differs from Sciurus in the form and position of the anteorbital foramen; in the greater obliquity of the plane of the zygoma and its more gentle downward deflection; in the more regularly oval, flattened, and depressed form of the skull, and especially in the skull being more narrowed anteriorly and in the nasal portion being more produced; in the molar series being divergent anteriorly inste
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