[4 1 .] 7. A rvicola (Georychus) trimucronatus. (Richardson.)
Back’s Lemming.
Arvicola trimucronatus. Richardson, Parry's Second Voyage, App. p. 309.
A> Georychtjs (trimucronatus) auriculis vellere sub-conditis, rostro nigro obtusiusculo, pa/mis pentadactylis unguibus (4)
lanceolatis curvis ; ungue pollicari ligulato tricuspidato, corpore super obscwrh castaneo, latere ferrugineo
suiter cinereo.
Back’s Lemming, with ears somewhat shorter than the fu r; a blunt, black nose; four daws on the fore-feet, of a
lanceolate form, and a strap-shaped thumb-nail, with three small points at the end; body, dark chestnut-
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
latitude 65°, on Captain Franklin’s first expedition. Mr. Edwards, the Surgeon
of the Fury, on Captain Parry’s second expedition, brought a specimen from
Igloolik, in latitude 69J°; 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. Ears shorter than the fur, inclined
backwards, thinly clothed. Eyes 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.
The Body is broad and rather flat, and is everywhere covered with a beautifully fine and
soft fur, which is about nine lines long on the back, but . rather shorter on the belly. The
colour of the head and dorsal aspect of the neck and shoulders is a mixed reddish-gray,
formed from the mingling of the clove-brown, yellowish-brown, and black tips of the hairs in
nearly equal proportion2. The back is chestnut-brown, but many of the longer hairs are tipped
with black. The sides are reddish-orange, and the belly, chin, and throat, gray, intermixed
with many orange-coloured hairs. The colours of this animal very strongly resemble those of
the Tawny Lemming ; but its nose is deep black, whilst the nose of the latter is pale. The
tail projects a few lines beyond the fur, is clothed with stiff hairs converging to a point, dark
above, grayish-white below.-
The fore-legs are short, but the feet are moderately large, and turned outwards, like the
feet of a turnspit dog. They are of a dark clove-brown colour above, and are clothed with
longer white hairs posteriorly. The (4) toes are naked underneath, and are armed with
moderate-sized strong nails, curved downwards, and inclined outwards. They are of an
oblong form, convex above, not compressed, are excavated, underneath more broadly than
the nails of any of the other American lemmings I have met with, and have sharp edges
fitted for scraping away the earth. The thumb is almost entirely composed of a strong nail
which has two slightly convex surfaces, a strap-shaped outline, and a truncated extremity,
from which three small points project. The palms are narrow.
The posterior extremities are considerably longer than the fore ones, the thighs and legs
being tolerably distinct from the body. The sole is narrow, long, and somewhat oblique,
having its inner edge turned a little forwards. The toes are longer, and the claws as long,
but more slender than those of the fore-feet, and they are much compressed. In the tawny
lemming (No. 40.) the claws of both the hind and fore feet are compressed.
Dimensions
Of a male killed at Fort Franklin.
Incites. Lines. Inches. Lines.
Length of head and body . K . 5 0 Length of fur on the back . . 0 9
,, tail . . , . 0 6 „ palm and claw of middle toe, nearly 0 6
head . . . . . 1 5 • ,, claw of middle toe 0 2
j ,, ears . • . 0 4 „ sole, and middle claw of hind-foot 0 9
,, whiskers . * . . 1 3
A female was only inches long.
Since this animal was described in the Appendix to Captain Parry’s Voyage, above quoted,
a second American species (A. helvolus), armed with a thumb-nail, has been discovered,
and the trivial name of Five-fingered American Lemming being no longer distinctive, I have
given it a new English appellation, after the officer who first procured a specimen.