478 



U. S. 1. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



List of specimens. 



1 Measured before skinning. Fore arm, .55 ; from elbow to end of claws, .90 ; longest fore and hind claws, each, .06 ; from knee joint to end of 

 claws, 1.42; tibia, .83; mammae 4 abdominal, two pectoral. 

 * Measured before skinning. 



HESPEROMYS CALIFORNICUS. 



Mus californicus, GAMBEL, Pr. A. N. Sc. Phila. IV, August, 1848, 78, (Monterey.) 



Sr. Cu. Very large. Size of third grown rat. Ears very long, angular. Tail rather longer than body. Color above, 

 sooty brown, passing on the sides to fulvous. Under parts white, tinged with fulvous and ashy. Feet white. Tail 

 brown, a littler darker on the dorsal line. Soles entirely naked. 



This is one of the largest, if not the largest, of the North American Hesperomys, with the 

 exception of the H. palustris of Georgia. The ears are enormously large, in this respect cer 

 tainly exceeding any other species ; they are considerably higher than broad, and, instead of 

 being rounded uniformly at the tips, are cut at nearly a right angle with the corners rounded. 

 They are uniformely coated with short white hairs, which do not form a fringe, as on Neotoma. 



The hind feet have the soles naked from the heel. The tail is considerably longer than the 

 body, very thick and stout, as in the rats. The fur is very soft and full. 



The middle of the back of this species is a mixed black and grayish plumbeous, the former 

 greatly predominating ; towards the sides there is less black, and light brownish yellow makes 

 its appearance, forming quite a conspicuous stripe on the lower part of the sides, less distinct 

 on the cheeks. The dusky extends to the wrist and heel, though the upper surfaces of the feet 

 are entirely white. The under parts are dull whitish, strongly tinged in places with fulvous, 



