HETEROMYID^ 161 



Perognathus with a large head and long hind feet; skuU similar 

 to Dip'odoniys, with the inflation of the temporal region carried to 

 the farthest extreme known among mammals ; zygomatic process 

 similar to that of Perognathus, not widely expanded in front 

 of orbit as in Perodipus and Depodomys; occipetal notch between 

 the enormously inflated mastoids proportionally deeper than in 

 any other genus of the family; supraoccipetal, interparietal and 

 parietals greatly reduced; hind feet long; soles densely haired; 

 five toes on each hind foot, the inner toe similar to that of 

 Perognathus in size and location; tail indistinctly bicolor, some- 

 what longer than head and body ; miammje six, one pair pectoral 

 and two pairs inguineal. 



Microdipodops calif ornicus Merriam. 



CALIFORNIA DWARF POCKET-RAT. 



Above grizzled yellowish olive; sides from nose to thighs 

 cream buff, forming an indistinct stripe; below dull white to roots 

 of hairs ; nO' white stripe across the thigh ; a dark crescent at 

 base of whiskers; an indistinct white spot above the eye; feet 

 grayish white; tail bicolor, dull buff below, buffy gray above, 

 darkening toward the tip; whiskers mostly blackish, the longest 

 reaching the shoulders. 



Length about i6o mm. (6.30 inches) ; tail vertebrse 92 

 (3.60); hind foot 25 (i). 



Type locality. Sierra Valley, Plumas County, California. 



The above description (except measurements) is drawn up 

 from a male that I caught in northwestern Nevada, five miles east 

 of the California boundary. This may vary a little from the 

 Plumas County animals. The only locality in California where 

 I know of Dwarf Pocket-Rats having been taken is Sierra Val- 

 ley, Plumas County. Animals of this genus have been taken in 

 various localities in Nevada and in eastern Oregon. The two 

 that I caught were taken in sandy land among sage brush, with 

 grain baited mouse traps. I know nothing further of their 

 habits. 



