brane is not so full as in the latter, and its border is straight. The end of the nose is hair-
brown, and the fur about the mouth and on the sides of the nose has a dark smoke-gray
cblour. The ears are thin and membranous in appearance, thinly covered on both sides
with short adpressed hairs, but having some fur at their base posteriorly, similar to that on the
adjoining parts of the head. Their form is semi-oval with rounded tips. The surface of the
fur on the back has a yellowish-brown colour, without any tendency to the more red hue of
the back of the. Pt. Sdbrinus. The fur of the throat and belly is a grayish-white, without
any tinge of buff-colour; the tail has a flat, oblong, oval form, and has a blackish-brown
colour above, and is merely paler beneath.
The extremities are shaped like those of Pt. Sabrinus, but are larger in proportion. The
soles, palms, and under surfaces of the toes, are well covered with fur, except a small callous
eminence at the end of each toe, five eminences on the palm of which the two posterior ones
are the largest, and four on the soles situated at the root of the toes. The brush of soft fur
near the outer edge of the soles is as conspicuous as in* the P t Sabrinus.
Dimension’s.
Inches. Lines
Length of head and body . . 8 0
head ■ . 2 2
„ tail (vertebrae) 5 3
| „ including fur . 6 3
,, palm, middle fore-toe and daw 0 10
: „ sole, middle hind-toe and daw 1 6
* • . . whiskers . . 2 6
Breadth between the outer edges of the flying
membrane . . . 4 9
Inches. Lines.
Height of the ears posteriorly . . 0 6
Dimensions of the scull.
Length from tip of nasal bones to occipital
ridge of nasal bones ► . 1 6
,, of nasal bones . . 0
Breadth at the posterior part of the zygomatic
process . . . '. - | . 1 0
Breadth of frontal bone between the orbits 0 &
There is a specimen in the Hudson’s Bay Museuin, which measures nine inches
from the end of the nose to the origin of the tail.
G eomys. (Rafinesque.) Sand-Rat.
Geomys. “ R a f in e s o u e -S m a l t z , Amer. Month. Mag, for 1817, P- 45.” D e s m a r e s t , Mamm., p. 314.
Lesson. Man. de Mammal., p. 260. -
Ascomys. Lichtenstein ? Saccomys. F. Cuvier ?
Pseudostoma. Say ?
P late xviii C. F ig. 1 to 6.
CHARACTERS.
Denial formula, incisors, §, canines jEs, grinders = 20.
Incisors strong ; linear and flattish anteriorly; narrower posteriorly, and chamfered away
evenly from their insertion into the sockets to their tips. The upper ones are generally
marked with one or more grooves anteriorly; the lower ones have sometimes a faint groove
on their exterior sides. The second and third pairs of grinders in each jaw are quite simple
in their structure, each tooth consisting merely of a slightly curved cylinder of enamel,
without roots, compressed from before backwards, with a longitudinal depression or shallow
furrow on one side, which it renders more acute than the opposite one; the acute side of the
grinders faces outwards in the upper jaw, and inwards in the lower one. The crowns of these
teeth are flat, and have a transversely pear-shaped area, composed of soft bone, enclosed by
a rim of enamel, but there are no transverse ridges. The posterior pair of grinders in each
jaw are not so much compressed as those just described, but are nearly cylindrical, and have
a roundish, slightly angular crown. The anterior pair, above and below, differ still more
widely from the rest in being double, each of them being composed of two cylinders,
shaped like the other teeth, and connected with each other by a narrow neck : the anterior
cylinder is smaller than the other, and the long diameter of its crown is parallel to the
axis of the jaw, and consequently is at right angles to the transverse pear-shaped crown of
the posterior cylinder, and to the crowns of the teeth which succeed it. The upper grinders
incline slightly backwards, the lower ones have a similar inclination forwards, and the grinding
surfaces of both are very even.
The lower jaw is particularly thick and strong, and its symphysis which slopes upwards
nearly in the same direction with the incisors is about one-third of its whole length. The
palate is very narrow, and in the scull exhibits a central longitudinal crest of bone, with a
deep and partially covered furrow on each side of it for the passage of vessels.
The head is large and depressed; the nose short. On examining the scull, the frontal
and nasal bones are observed to be in the same plane, and the zygomatic arch is but a
little depressed below the crown of the head.
The nostrils are small round openings, facing downwards and somewhat laterally, separated