554 
U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY—GENERAL REPORT. 
MYODES, Pallas. 
Lemmings. 
Myodes, Pallas, Zoog. Rosso—Asiatica I, 1811, 172. 
Fore feet large ; its claws very long, fossorial, longer than the hinder. Soles (and palms?) hairy to the roots of the toes. Tail 
shorter than the hind foot. Skull very broad ; the zygoma high. Posterior lower molar composed of four subtriangular prisms, 
the anterior of not more than five. Root of lower incisor not passing beyond or under the posterior molar, as in Jlrvicola. 
The Lemmings , with the same general appearance as the Arvicolas, can he readily distinguished 
externally, by the more or less hairy soles, very short tail, and long sickle-shaped claws, fitted 
for digging, the external ear either very small, or altogether wanting. The last lower 
molar is composed of four or five triangular prisms which alternate with each other as in Fiber , 
instead, as in Arvicola, of having three prisms composed of a greater number of triangles 
placed with their bases opposite each other and confluent, (the indentations opposite also,) and 
the tooth exhibiting therefore only three prisms, or three islands of dentine. 
The species of this genus are confined to the arctic regions of the northern hemispheres. 
Three or four species belong to North America, but none have yet been found within the United 
States. 
Not having.access to all the authorities, I am unable to say whether the name of Myodes or 
Lemmus should be retained for this group. Pallas includes the Arvicolae with the Lemmings 
in establishing Myodes ; and it is to Keyserling and Blasius that we owe the restriction of the 
name. It is possible that Lemmus was established by Linck after Myodes , and with the same 
wide application ; in which case Myodes will be left for the Lemmings ; Arvicola having been 
made by Lacepede in 1803 for the genuine field mice. 
In any event the name of Georychus, used by Richardson and Audubon and Bachman, is 
inapplicable to the true Lemmings, as it was constructed by Uliger to receive the cape rat of south 
Africa, Georychus capensis ; which, however apparently similar in external form, is so essen¬ 
tially distinct as to belong to an entirely different family. 
In the absence of any specimens of typical Myodes from America, I am obliged to select one 
of the European species for the illustration of the genus. Of the four species in the collection 
of the Smithsonian Institution, M. lemmus, torquatus, obensis, and schisticolor , I choose the 
first mentioned as the best known type. 
The body is stout; the head very broad and short; the legs are short and strong ; the tail 
shorter than the hind foot. The hair is very coarse and bristly. 
In the general character of the muzzle Myodes agrees with Arvicola. According to Keyser¬ 
ling and Blasius, the whiskers are arranged in five horizontal series. The ears are short and 
orbicular, and margin narrowly the large auditory aperture. They are thickened and nearly 
naked ; very sparsely coated with short whitish hairs. (In M. lemmus they project above the 
head .2 of an inch; in some species they are much shorter.) There is no antitragus at all 
prominent, as in the Arvicolae. 
The feet are short and strong ; the fore feet much developed in size, measuring with the claws 
as much as the hind feet without them. The fore claws are very long, stout, and fossorial; 
considerably longer than the posterior. The palms are naked. The thumb is very short, 
nearly obsolete, armed with a compressed elongated strap-like nail, truncate at the end, .15 of 
