RODENTIA-ARVICOLINAE-MYODES. 
559 
figuring the variations of color, the osteology, &c. The animal is strictly circumpolar, coming 
further south, along Behring’s Straits, than elsewhere. The N. P. Exploring Expedition, 
under Captain Rogers, collected specimens on the island of Arikamtchichi, in Behring’s Straits, 
near the Asiatic shore. 
Myodes obensis, Brants. 
Myodes obensis, Brants, Muizen, 1827, 55. 
Keyserling & Blas. Wirb. Europ. 1840, YI, pp. vii and 32. 
Middendorff, Sibirische Reise, II, ill, 1853, 99 ; pi. ii, figs. 7-9 ; pi. viii, ix. x. f. 2, 
Arvicola {Georychus?) helvolus, Rich. F. B. A. I, 1829, 128. 
Georychus helvolus, Aud. & Bach. N. Am. Quad. Ill, 1853, 84 ; pi. cxx, f. 1. 
Arvicola ( Georychus) Irimucronalus, Rich. Parry 2d voyage, 1825, 309.—Ib. F. B. A, I, 1829, 130. 
Georychus trimucromtus, Aud. & Bach. N. Am. Quad. Ill, 1853, 86, pi. cxx, figs. 2. 3. 
Myodes alligvlaris, Wagner, Suppl. Schreber, III, 1843, 602. 
This species is distinguished prominently from the preceding, according to Richardson, by 
the existence of a strap-shaped nail (claw?) to the thumb, instead of having the thumb very 
rudimentary, and without any nail. 
The remaining species of myodes found in the Old World are ill. lemmus, in Norway and 
Sweden, the typical Lemming of old authors; M. schisticolor, in Norway, and recently obtained 
on the west coast of the sea of Ochotsk, and M. lagurus , on the Ural river, and the steppes of 
Grand Tartary. Good specimens of all the known Old World species are in the collection of 
the Smithsonian Institution, with the exception of M. lagurus. The following diagnosis of the 
species is taken chiefly from Keyserling and Blasius. 
a. With a sharply defined dark dorsal stripe from the middle of the crown to the tail. 
1. A whitish collar, bordered before and behind with brown. (Very obsolete in 
some specimens.) Above, watered with pale yellow and reddish brown; paler on 
the sides. Beneath, whitish. Whiskers black. torquatus. 
2. Without white collar. Above, pale gray, mixed with dark brown hairs. 
Beneath,whitish gray. Upper whiskers brownish, lower whitish. lagurus. 
b. Without a sharply defined dark dorsal stripe. 
3. Above, uniform brownish yellow, mixed with black hairs; the sides brighter 
yellowish. Under parts and legs, pale rust-yellow; toes and feet yellowish white; 
throat white. ...obensis. 
4. Black areas on the rusty red ground of the upper parts. Head, neck, and anterior 
part of the hack brownish black; the hinder half of the hack and the remainder 
of the upper part of the body with irregular black spots. Two elongated spots of 
yellowish red between the ears; beneath, rusty yellow; toes, dark brown; feet, 
yellowish. lemmus. 
5. Nearly uniform slaty plumbeous all over, with a reddish spot on the hack. Fore 
claws but little developed... schisticolor. 
