FIELD BOOK OF MAMMALS 



Upperparts pale mouse-gray, head and back darker than 

 sides, mixed with ochraceous buffy; a pale ochraceous buffy 

 lateral line; feet white; forearms grayish on outer sides; tail 

 above, dusky, below, white, tip dusky above and below; 

 underparts white. 



Measurements. — Sexes of equal size. Total length, 9.5 

 inches; tail vertebras, 5 inches; hind foot, 1.2 inches. 



Geographical Distribution. — From southern Texas south 

 into Mexico, in lower Sonoran Zone on low plains. This 

 genus is southern in its distribution and only the one form 

 ranges far enough north to cross the Rio Grande. 



Food. — Largely seeds. These are of great variety, chiefly of 

 weeds and native flowering plants, but may include domestic 

 grain such as wheat and corn. The diet is varied by small 

 amounts of green vegetation and twigs. 



Enemies. — Owls, Weasels, Foxes, Coyotes, Cacomistles. 



Having had no experience with the North American Spiny 

 Pocket Rats, I quote from Bailey, Biological Survey of Texas, 

 North American Fauna, No. 25, 1905, page 127. 



"Loring reports them at Brownsville as 'common in the 

 timber under logs and the roots of trees;' and Lloyd says 

 they are 'found at Lomita in the densest brush on the ridges 

 forming the old banks of the river, and around old corrals.' 

 He adds: 'Their habit of throwing out a white clayey mound 

 like the gophers attracts attention, and, although the mound 

 may be a month old, by cleaning out a hole and putting a 

 trap in it you will in time capture the occupant. The ordinary 

 outlets are generally covered up by fallen leaves, which in 

 some instances seem to have been placed there by the occu- 

 pants. They are strictly nocturnal in their habits, and feed 

 on the seeds of hackberry, mesquite, and various other shrubs. 

 Young and old inhabit the burrows together.'" 



Genus Perognathus ^ 



Dentition: Incisors, J ; Canines, ^ ; Premolars, {; Molars, f =20. 



^ For a revision of this genus see W. H. Osgood, North American 

 Fauna, No. i8, 1900. Many forms have been described since this was 

 written. 



298 



