130 NORTHERN ZOOLOGY. 
[41.] 7 Arvicota (Grorycuus) TRimucronatus. (Richardson.) 
Back’s Lemming. 
Arvicola trimucronatus. Ricwarpson, Parry’s Second Voyage, App. p. 309. 
A, GEonycuus (trimucronatus) auriculis vellere sub-conditis, rostro mgro obtusiusculo, palmis pentadactylis unguibus (4) 
lanceolatis curvis ; ungue pollicari ligulato tricuspidato, corpore super obscure castaneo, latere ferrugineo 
subter cinereo. 
Back’s Lemming, with ears somewhat shorter than the fur; a blunt, black nose; four claws on the fore-feet, of a 
lanceolate form, and a strap-shaped thumb-nail, with three small points at the end; body, dark chestimut~ 
colour above, reddish-orange or rust-colour on the sides, and gray beneath. 
This animal was discovered by Captain Back on the borders of Point Lake, in 
Jatitude 65°, on Captain Franklin’s first expedition. Mr. Edwards, the Surgeon 
of the Fury, on Captain Parry’s second expedition, brought a specimen from 
Teloolik, in latitude 693°; and specimens were obtained on Captain Franklin’s 
last expedition on the shores of Great Bear Lake. At the latter place it was found 
in the spring, as soon as the ground began to thaw, burrowing under the mossy 
turf. In the winter it travels under the snow in a semicylindrical furrow, very 
neatly cut to the depth of two inches and a half, in the mossy turf. These hollow 
ways cross each other at various angles, but occasionally run to a considerable 
distance in a straight direction. From their smoothness, it was evident that they 
were not merely worn by the feet, but actually cut by the teeth. Their width is 
sufficient to allow the animal to pass with facility. The food of this Lemming 
seems to consist entirely of vegetable matters. It inhabits woody spots. A female 
killed on Point Lake, June 26, 1821, contained six young, fully formed, but 
destitute of hair. 
DESCRIPTION, 
Size, a little inferior to the Hudson’s Bay Lemming, or nearly about that of the Norwegian 
Lemming. Head flat, covered by moderately long fur. ars shorter than the fur, inclined 
backwards, thinly clothed. H'yes smaller than those of the English domestic mouse. Upper 
lip deeply cleft. The nose is obtuse, with a small, naked, but not pointed or projecting tip, 
and covered above with hairs of a deep black colour. Whiskers numerous, black at the roots, 
brownish or white at the extremities ;-some entirely white. Inside of the mouth hairy, the 
hairs springing from projecting glandular folds. Teeth—incisors, somewhat yellowish ; upper 
ones presenting a conspicuous, but shallow groove, with an obliquely notched, cutting edge. 
Grinders, three on a side in each jaw. 
