FIELD BOOK OF MAMMALS 



ally four or five. Several litters may be raised in a year over 

 most of the range of the genus, although the northern forms 

 probably rear but one family a season. 



While most of the species of Pocket Mice are common 

 mammals in their respective ranges, there are forms of this 

 genus which are among the rarest of the North American 

 rodents. For some unknown reason the distribution of these 

 particular creatures is very local and only at long intervals are 

 specimens taken. Such a form is the Pacific Pocket Mouse, 

 Perognathus pacificus, one of the smallest of rodents. 



Genus Dipodomys^ 



Dentition: Incisors, \; Canines, {j ; Premolars \; Molars,f = 20. 



Kangaroo Rat. — Dipodomys agilis 



and related forms 



Names. — Kangaroo Rat; Pocket Rat. Plate XXVI. 



General Description. — A small Rat with elongated hind 

 legs and short forelegs ; hallux greatly reduced or absent ; long, 

 tufted tail; rather robust body; large head; large eyes; rounded 

 ears; external, fur-lined cheek-pockets; long, soft pelage; 

 distinctive and attractive color pattern ; progression by means 

 of kangaroo-like hops, the small forelegs not touching the 

 ground; hind feet and toes furred on under surface; nocturnal 

 in habit. 



Color. — Sexes colored alike; seasonal variation not very 

 great. 



Upperparts. — Dusky cinnamon-buff; sides clearer in tone 

 than back and meeting white of underparts in a sharp line; 

 pelage slate-gray basally ; blackish patch at base of whiskers on 

 each side, joined over the nose by a dusky crescentic bar; eyelids 

 blackish; buffy white area between eye and dark whisker- 

 patch, and a light spot over eye; a silky white patch of hairs 

 semi-concealed at posterior base of ear; ear blackish brown, 

 with white spot at anterior base; longer whiskers blackish, 

 shorter whiskers whitish; thigh marked by a sharp band of 



^ No recent revision of this genus has been published, but the reader 

 is referred to A Geographical Study of the Kangaroo Rats of California by 

 Joseph Grinnell, Univ. of California Publication in Zoology, Vol. 24, No. 

 I, pp. 1-124, 1922. This paper gives full data on more than half of the 

 forms treated in this handbook. 



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