SCIURIDA—ARCTOMYS MONAX. ; 911 
Spermophilus, differing scarcely more from Sciurus than do the Otospermo- 
philine forms of Spermophilus. Ou the other hand, it is in these features 
that Cynomys is highly specialized. The skull of Arctomys, viewed in its 
totality, differs from the Sciurine forms of Spermophilus mainly in its very 
much larger size, and in its much straighter dorsal outline. This, in part, 
results from the depression of the interorbital region, and in part from the 
great development of the occipital crests, naturally correlating with the large 
size and heavier form of the animal. The triturating surface of the molar 
teeth in Arctomys presents two deep transverse grooves, extending from the 
outer edge to the middle of the tooth, instead of three, as in Cynomys, 
agreeing in this respect with Spermophilus, Tamias, and Sciurus. The first 
upper premolar is relatively not larger than it usually is in Spermophilus, and 
is smaller, absolutely as weil as relatively, than in Cynomys. 
The genus Arctomys embraces the largest members of the Sciurida, 
and, excepting Castor, the largest of the existing North American Rodentia. 
The group is represented throughout the northern and middle portions of the 
northern hemisphere, and is not found elsewhere. In the present paper, 
three species are provisionally recognized as North American and as distinct 
from their nearest Old World allies. 
ARCTOMYS MONAX (Linn.) Schieber. 
Woodchuck. 
Mus monax Linnxvs, Syst. Nat. 10th ed. i, 1758, 60; 12th ed. i, 81 (based wholly on Edwards's descrip- 
tion and figure of a specimen from Maryland).—Pa as, Nov. Spec. Glires, 1778 (in part 
only).—Bopp art, “ Elench. Anim. i, 1784, 105,” 
Glis monax ERXLEBEN, Syst. Anim. 1777, 361 (in part only). 
Arctomys monax SCHREBER, Siiuget. iv, 737.—Suaw, Gen. Zool. ii, 1808, 117.—F. Cuvier, Dict. des Sci. 
Nat. xxix, 1823, 162.—WanrpEN, Descrip. des Etats-Unis, v, 1820, 627.—Drsmarest, Nouv. 
Dict. d’Hist. Nat. xix, 1818, 314; Mam. 1822, 328 (in part only).—Sapineg, Trans. Linn. Soe. 
xiii, 1822, 582.—Harvan, Faun. Amer. 1825, 158.—Gopman, Amer. Nat. Hist. ii, 1826, 100.— 
I. Georrroy, Dict. Class. d’Hist. Nat. x, 1827, 186—Haminron-Smiru, Griflith’s Cuvier’s 
An. King. iii, 1827, 170 (with plate); v, 1827, 244.—Ricuarpson, Faun. Bor.-Amer.i, 1829, 
153 (compiled, chiefly from Godman).—FiscuEr, Synop. Mam. 1829, 342.—EmMMons, Quad. 
Mass. 1840, 64.—Dr Kay, New York Zodl. i, 1842, 65, pl. xxi, fig. 4—THomrson, Nat. Hist. 
Vermont, 1842, 44.—WaGner, Suppl. Schreber’s Siiuget. iii, 1843, 259 (in part).—Scuinz, 
Syn. Mam. ii, 1845, 61—AupuBoN & BacuMan, Quad. N. Amer. i, 1849, 17, pl. ii —GIEBEL, 
Siiuget. 1855, 629 (in part ouly ; includes all the American species).—K®eNNIcoTT, Trans. Ill. 
State Agr. Soc. i, 1855, 579; U.S. Pat. Off. Rep. Agr. 1856 (1857), 82, pl. x.— Barrp, Mam, 
N. Amer. 1857, 339, pl. xlix, fig. 1 (skull).—Tuomas, Trans. Il]. State Agr. Soe. iv, 1860, 657.— 
Ross, Edinb. New Phil. Journ. xiii, 1861, 162; Canad. Nat. and Geol. 1861, 434; Nat. Hist. 
Rey. 1862, 274.—Maxrmivian, Arch. f Naturgesch. 1861, 93.—ALLEN, Bull. Mus. Comp. Zool. 
i, 1869, 226 (Massachusetts) ; Proc. Bost. Soc. Nat. Hist. xiii, 1¢70, 190 (lowa); xvi, 1874, 
- 294.—Corr, Proc. Amer. Phil. Soe. Phila. xi, 1869, 173 (fossil; bone-caves, Virginia).—GIL- 
PIN, Proc. and Trans. Nova Scotia Inst. Nat. Sci. ii, pt. iii, 1870, 16.—Apams, Field and For- 
est Rambles, 1873, 100, 296 (New Brunswick). 
