bushy tail» densely hairy, instead of a round tapering* one, scaly and thinly hairy.
In the softness of its fur, and general arrangement of its colours, it has much
similarity to the common wood-rat. It differs, however, from the genus mus, as
now restricted, in the form of its teeth, approaching more nearly to the genus
arvicola in that respect than to any other, but receding from it, on the other hand,
in the length of its tail, limbs, and in its general light, active form. Besides the
specimen brought home by the Expedition, and from which the accompanying
very correct engraving by Landseer was executed, there is another good
specimen in the Museum of the Hudson’s Bay Company; a third, with a mutilated
tail, in the Zoological Museum; and a fourth, without a tail, and much overstuffed,
in the British Museum, all said to have come from the same quarter. I
have also a hunter’s skin, of a larger, and perhaps a specifically distinct kind,
procured on the Rocky Mountains in latitude 63°.
D E S C R I P T IO N .
In size, this Neotoma equals the Norway rat, and it has a good deal of the character of
that animal in its physiognomy. Its nose is compressed and narrow, but appears rather-
obtuse if viewed laterally. There is a very narrow, naked margin to the nostrils, the tip and
sides of the nose being covered with short hairs. The upper lip is divided about three
lines deep.
Dental formula, incisors ■§, canines 5=5, grinders §§| = 1 6 .
The incisors have: precisely the form of those; of the meadow-mice, and wear away in the
same manner at their points. The upper ones are short, slightly rounded, and not grooved
on their anterior, surface; The lower ones are-long, narrow, and rounded anteriorly and
on the sides. The molar teeth also very much resemble those of a meadow-mouse. {A.
xanthognathibs). The grooves on their sides, however, instead of running to the base of
the tooth, terminate abruptly, where it is immersed in the so ck e ta n d some little distance
below this termination, most of the grinders divide into two fangs. The two anterior pairs
of lower grinders have these fangs very distinct, the space between the fangs being deep
and wide; but the upper grinders and the-posterior pair in the lower jaw have them much
shorter, and as it were coalesced- The first grinder in the upper jaw has the rudiments of
three fangs. The grinders of both jaws have a slight inclination backwards, and they gradually
decrease from before backwards in size, and in the height of the part which projects above
the sockets, preserving however an even grinding surface. In the upper jam, the first
grinder has three grooves, on its exterior side, and as many inside, with an equal number of
rounded projecting columns or ribs of a side; the second and third grinders have each two
grooves, with three ribs exteriorly, and one groove with two ribs interiorly. In all, there
are nine ribs on the exterior sides of the upper rows of grinders, seven on the interior sides,
•end ten triangles, formed by the folds of enamel on their crowns. In the lower jaw, the first
-grinder has two grooves exteriorly, and three interiorly; the second has two grooves on each
side, and the third, one on each side. In all, there are nine ribs on the outsides, and eight on
the insides of the lower rows of grinders, and nine triangular folds of enamel on their crowns.
These triangles are disposed in a single series, or at least.present, very obscurely, the double
alternate arrangement which exists on the crowns of the grinders of the meadow-mice. The
grinders of a Neotoma further differ from those of the meadow-mice in the ribs on their sides
being broader and more rounded, and in the first upper grinder, instead of the last one, being
the largest. The whiskers are considerably longer than the head ; the anterior ones are
white; the posterior ones, which are longer and stronger, are black, more or less tipped
with white. The ears are large, oval, and rounded, closely covered on the back with
short, adpressed, blackish-gray hairs, and they have a very narrow and obscure white margin.
Their anterior surface is more sparingly hairy above, and is quite naked near the auditory
opening.
The fu r is remarkably fine, soft, and long, and has considerable lustre. The upper parts,
including the head and cheeks, back, sides, and outer surface of the fore and hind thighs and
legs, have a nearly uniform, light, yellowish-brown colour, intimately mixed with black hairs;
the resulting tint is between a hair-brown and a fawn colour. The black hairs are more
abundant on the sides of the nose, down the middle of the head and back, and about the
rump. The upper lip, chin, throat, all the under parts, the inside of the thighs, and the
whole of the feet, from the wrist and ankle joints, are pure white. The fur is longest on
the back and sides, a little shorter on the belly, and shortest about the nose, but the furry
coat is close throughout, and is everywhere of a deep blackish-gray colour for two-thirds
of its length from the roots.
The tail at its commencement is cylindrical, and clothed with shorter hairs ; but the fur
gradually lengthens towards its extremity, where it is -upwards of an inch long, and is
somewhat dlstichously arranged, particularly beneath. The whole- of the fur of the tail is
very close and woolly at bottom. For a short space next the rump, the tail is coloured above
like the back ; but for the greatest part of its length it is of a dark lead-gray, arising from
an intimate intermixture of blackish-gray and whitish hairs. Underneath it is throughout of
a white colour, and when the tail is spread out, the white hairs form to it an indistinct
white tip.
The feet are thickly clothed above with fur, which conceals the claws. On the fore-feet
there are *four toes, which do not differ much from each other in length, the two middle ones
being longer only in a very slight degree. There is a small callus in place of a thumb, which
Is situated behind the roots of the'toes, and is »protected by a minute adpressed nail. There
•are besides five callous eminences of considerable size on the palm; three arranged in a
triangular form at the roots of the toes, one a little longer posterior to the thumb tubercle,
and another of equal size opposite to it. The claws are white, short, much curved, and
very acute. The hind-feet have five toes, the four anterior of which much resemble those