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. 



KEYSERMNQ & BLAS. Wirb. Europ. 1840, VI, pp. vii and 32. 



MIDDENDORFF, Sibirische Reise, II, in, 1853, 99 ; pi. ii, figs. 7-9 ; pi. viii, ix. x. f. 2, 

 Arvicola (Georychus ?) helvolus, RICH. F. B. A. I, 1829, 128. 

 Georychus hdvolus, AUD. & BACH. N. Am. Quad. Ill, 1853, 84 ; pi. cxx, f. 1. 

 Arvicola (Georychus) Irimucranatus, RICH. Parry 2d voyage, 1825, 309. IB. F. B. A, I, 1829, 130. 

 Georychus trimucronatus, AUD. & BACH. N. Am. Quad. Ill, 1853, 86, pi. cxx, figs. 2. 3. 

 Myodes albigularis, 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 M. 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. laguius, 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 de/tned 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 back brownish black ; the hinder half of the back and the remainder 

 of the upper patt 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 back. Fore 



claws but little developed schislicolor. 



