356 U. 8s. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
the muffle is separated, by a considerable interval, from the edge of the upper lip ; this interval 
entirely covered with short hairs. The upper lip is acutely emarginated, though scarcely 
bifid ; there is no naked groove running up to the muffle. There are no cheek pouches. The 
hairs of the lips extend a short distance on their inner surface, but do not pass into the cavity 
of the mouth, as in some rodents. The tongue is very large and fleshy. The eyes are 
excessively small, the iris not two lines in diameter ; their centres about midway between the 
end of the snout and the auditory aperture. The ears are moderately developed, thick, and 
nearly orbicular, densely covered with hair on both surfaces, the hairs extending even into the 
meatus. The bristles are in five horizontal series, about five in each series; the upper row, 
however, with only one or two. 
The limbs are large and stout ; the under surfaces of all the feet entirely naked ; the upper 
surfaces coated with short stiff silky hairs ; the fore claws are about as large as the hinder ones. 
The hand has five very distinct fingers, each with well developed claws; the third finger is 
longest, the fourth a little shorter ; then the second and the fifth ; the claw of the first reaches 
as far as the cleft between the third and fourth. There are only two tubercles on the palm, 
both large, and placed side by side; the exterior twice as large as the interior, and extending 
further back. The hind feet are very large and turtle-like; their plane oblique to the body. 
All the toes connected by a thickened web, extending between their very tips; this web is 
naked on the upper side between the toes, and when fully extended the foot appears nearly 
twice as broad as long. ‘There are but faint indications of broad flattened tubercles at the base 
of the toe. The claws are hollowed out beneath, with the sharp edges a little inflexed; they 
are curved and rounded. There is a kind of second claw under the claw of the second toe, of a 
rather hard horn-like substance, compressed and sharp-edged above where it fits into the con- 
cavity beneath of the true claw; in shape, it is not unlike a compressed grain of wheat. The 
sole is naked to the posterior part of the heel, and, with the palm and digits generally, is 
slightly fringed with short stiff hairs. The tibia is very slightly free, being closely united by 
muscle to the femur. 
The tail is really as long as the body without the head, though it is so thick for more than 
one-third from the base that its commencement can scarcely be made out ; for this distance it 
is conical and densely coated with hair, when it suddenly becomes very flat and much depressed ; 
the sides somewhat parallel to near the end, where they round off, the shape strongly resembling 
that of a mammal’s tongue. This portion is entirely covered with transversely elongated 
subhexagonal scales, of which about 110 to 120 series may be counted on the upper side, and 
some twenty transversely over the middle of the tail; the arrangement is in quincunx, with 
tolerable regularity on both sides, and there are short downy hairs projecting between all the 
scales, obscuring but not concealing them. 
The principal points in the external form of the beaver, and which may be considered 
as of generic signification, are the depressed, flattened and very broad tail covered with scales ; 
all the feet naked beneath, with five toes each, with a distinct claw; the hind feet completely 
webbed ; upper lips but slightly cleft, hairy with no groove; muffle naked; eyes very small ; 
bristles in five series. 
The color of the beaver varies considerably in different specimens, even of the same locality, 
the usual color being a reddish brown, sometimes quite dark, and again of rather a light 
yellowish tint of the same; I have heard of skins nearly black, and albinos are by no means 
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