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nostrils are lateral, the whiskers sparse, but some of them nearly half as 
long as the body. The cylindrical tail tapers uniformly to a fine point, 
with a slight pencil of hairs at the tip; it is covered with verticillate 
scales, with short hairs springing from beneath the whorls, but not con- 
cealing them. The eyes are small, situated midway between the nose 
and ear. The ear is remarkable among rodents for the development of 
the antitragus in the form of a circular, thickened pad, completely re- 
versible, and capable of being applied against the meatus; the tragus 
expands into a thin, free, rounded border, which may lie in apposition 
with the opposite antitragal lobe, thus providing for the perfect closure 
of the meatus. The hands are large, the thumb rudimentary, covered 
with a broad, truncated nail; the third and fourth fingers longest. The 
lengthening of the hind limbs, which determine the saltatorial habits 
of this species, is effected by the elongation of both the crasand the pes ; 
the former is longer than the latter. The toes are five, the secoad, third, 
and fourth sub equal, and much the longest; all have claws. The meta- 
tarsals are five, complete from end to end. (Coues.) The foot is covered 
above with short, silky hairs, below naked; the sole is smooth about half 
way, then grauular; the digits are transversely scutellate below. The 
general pelage is coarse and hispid, with but little gloss; bristly hairs 
are mixed with the soft, under fur. The under parts are snowy white, 
sharply separated from the sandy-yellowish of the sides and outer sur- 
faces of the limbs. There is a dorsal strip of brownish-yellow, heavily 
shaded with brownish-black ; this is about as wide as the lateral stripes 
already described. The tail is bicolor, corresponding to the body-areas ; 
the ears have a light-colored rim; the backs of the hands and feet are 
whitish ; the whiskers are mostly black. 
FAMILY MURID A. 
The family Muridx includes Rodents, which have the incisor teeth =} ; 
canines and premolars absent; molars $3; equal sixteen teeth in all. 
Tibia and fibula united below. The coronoid, condylar, and descending 
processes of the mandible are well developed and distinct. The ante- 
orbital foramen is a large pyriform slit, bounded exteriorly by a broad 
plate of the maxillary; this character is probably diagnostic of the fam- 
ily. The American genera are incluaed in two sub-families : 
Murinz.—Animals which include and resemble the comtiona Rats and 
Mice. The molars are rooted, tubercular, and with crenate periphery. 
Incisors compresséd, narrower than deep; root of outer incisor causing a 
protuberance on outer side of mandible; descending process of the man- 
dible, a broad flattened plate, wholly below the plane of the molars; pal- 
