910 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
Generic cuArs.—Skull with the dorsal outline nearly straight; frontal 
region flat or depressed; postorbitals triangular at base, with a long, spread- 
ing, decurved point; zygomatic arches moderately expanded, not widening 
and diverging posteriorly; grinding-teeth rather small, the transverse and 
antero-posterior diameters about equal, and the molar series very nearly 
parallel; occipital and interparietal crests well developed (in old age) ; ante- 
orbital foramina subtriangular, widest below, but not thrown outward. Size 
large; body thick-set, broad, depressed; cheek-pouches small; tail rather 
short, bushy, not flattened; ears small; nail of pollex broad, flat, or wanting ; 
pelage with long coarse hairs and thick under fur. Coloration generally yel- 
lowish-gray, without either distinct spots or stripes. 
The genus Arctomys differs from Cynomys in many quite important 
features. In Arctomys, the dorsal outline of the skull is straight, or nearly 
so, instead of highly arched, as in Cynomys; the zygomatic arches are rela- 
tively smaller, and reach their greatest expansion near the middle instead of 
at their posterior border; the grinding-teeth are small, in nearly parallel series, 
and differ widely from those of Cynomys in shape and in mode of insertion. 
In Arctomys, the molars are inserted nearly vertically, as in the true Squirrels; 
in Cynomys, their insertion is quite oblique. In Arctomys, the triturating 
surface of the crowns is nearly square, but the inner border is somewhat 
narrowed, so that the teeth of the same series touch each other by their 
crown surfaces for only two-thirds of their transverse breadth; in Cynomys, 
the transverse breadth of the crowns is twice that of the antero-posterior, 
and internally the teeth are so much narrowed that they abut closely for only 
half their transverse breadth, leaving internally deep openings between the 
teeth. In Arctomys, the palate is broad and scarcely narrower at the last 
molar than anteriorly, while in Cynomys the palate is rapidly and greatly 
narrowed posteriorly. Hence Arctomys differs very widely from Cynomys in 
respect to the size, form, and position of the molar teeth and the form of the 
bony palate. In all these points, Arctomys is more Sciurine than is even 
ordres, genres et espéces qui sont nommés dans cet ouvrage [Dents des Mammiféres], avec une syno- 
nymie latine”, occurs the following :— 
“54. Marmottes, arctomys. Gmel. 
““Marmoite des Alpes, Arctomys alpinus. Linn. 
“Marmotte du Canada, Arctomys empetra. Pall.” 
What he means by “ Arctomys cmpetra Pall.” is certainly not clear, s.nce no original description of 
Pallas’s empetra had at this date (1825) appeared, except Pallas’s original account of his Mus empetra. 
Sabine’s Arctomys empetra (1822) is Arciomys monax. If Cuvier had specimens of the ‘Marmotte du 
Canada”, his “ Arctomys empetra Pall,” is doubtless also referable to 4. monax. 
