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U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY-GENERAL REPORT. 
Cricetodipus .—Smaller. Ears small, without any lobe to the antitragus. Soles covered 
with short hairs on the posterior half. Tail rather scantily haired ; not tufted at tip. 
The species may he arranged under these divisions as follows : 
Perognathus. 
A. Tail crested above at the end. 
1. Sides without a lateral fulvous stripe. Size that of Hesperomys leucopus . penicillatus. 
B. Tail simple. Sides with a fulvous stripe. 
2. Larger than H. leucopus. Ears large. Above, sandy yellow. Outside of fore 
legs and upper surface of feet white. fasciatus. 
3. Size of H. leucopus , or less. Ears small. Hairs very rigid. Above, mixed 
cinnamon and black. Outside of both fore and hind legs, with the upper 
surfaces of the feet, white. . hispidus. 
4. Bather smaller than the preceding. Ears small. Above, cinnamon and 
black. Lateral stripe indistinct; outside of both fore and hind legs like the 
hack. monticola. 
Cricetodipus. 
5. Tail not longer, if as long, as the head and body. Hind foot about one-fourth 
as long as head and body. favus. 
6. Tail longer than the head and body. Hind foot more than one-third as long 
as head and body. parvus. 
The species of Perognathus have thus far been found from the lower Bio Grande of Texas to 
Eort Union, Neb., and westward to the Pacific ocean. 
PEBOGNATHUS PENICILLATUS, Woodhouse. 
Perognathus penicillatus, Woodhouse, Pr. A. N. Sc. Phila. VI, Dec. 1852, 200.— Ib. Ia Sitgreaves’ Expl. Zuni & 
Colorado, 1853, 49 ; plate iii, mammals. 
Aud. & Bach. N. Am. Quad. Ill, 1854, 298. 
Sp. Ch.—L arger than Hesperomys leucopus. Ears rather large ; antitragus lobed. Tail longer than the body ; upper side 
with a penicillated crest at the extremity. Feet large ; soles naked. Color above yellowish brown. Under parts.of body, 
hind feet, and entire fore legs to shoulder, white. Tail brown, whitish beneath to within an inch of the end ; no fulvous 
lines on the sides. 
This species is among the largest of the genus, and in many of its characters approaches 
closely to Dipodomys. It is about the size of Hesperomys leucopus, or larger. The head is 
broad, depressed, and acute. The muzzle is not cleft beneath, and is densely hairy everywhere, 
except on the septum and inner margin of the nostrils. The openings of the external cheek 
pouches are shorter than in P. fasciatus. The whiskers are very long, some of them reaching 
to the middle of the body. The ears are large for the genus, thin, and sparsely coated with 
hair ; larger and less hairy than in P. fasciatus. The antitragus is very distinct as a small 
rounded lobe. The opening of the ear is covered by a tuft of stiff bristly hairs. The fur is 
remarkably coarse and stiff, without any short wool or fur mixed with the longer hairs. The 
