152 University of California Publications in Zoology. [Vov-5 
the alfalfa patch on Johnston’s ranch at Cactus Flat, August 15. 
The above determination is by no means certain. The skins are 
extremely pale, almost precisely the same in coloration as ex- 
amples from Victorville, whence I have specimens identified by 
Vernon Bailey as perpes; but skull comparison with adult speci- 
mens might show decided differences, possibly in the direction of 
perpallidus. 
Perodipus agilis (Gambel). Gambel Kangaroo Rat. 
We detected this species at only one point in the region, 
though it or a closely related form is to be expected on the Upper 
Sonoran foothills of the Pacific side of the mountains. At the 
north base of Sugarloaf, on the sage-covered alluvial fan sloping 
to the northward, we saw a few signs, such as tail-marks, on dusty 
places between the bushes, and succeeded in trapping three adults 
August 23,1905. This was at an altitude of fully 7500 feet, but 
the zonal complexion is strongly Upper Sonoran, a tongue of this 
zone extending southwestward from the desert slope three miles 
away. This species must, however, have invaded into this region 
by way of Bear valley; for it is not a desert species. 
The three specimens obtained seem to me extremely similar 
to agilis from the vicinity of Los Angeles, the type-locality. They 
certainly cannot be referred to the recently named Perodipus 
stephensi which Merriam (Proe. Biol. Soe. Wash. XX, July 22, 
1907, p. 78) deseribes from San Jacinto valley; nor do they 
approach streatori closely. Yet there are slight differences char- 
acterizing them: their ears are perceptibly larger than in agilis, 
and not so sooty; the tail is crested further towards the base; 
the sides are paler tawny; and the skull appears to be broader. 
Close serutiny by one familiar with this genus and its features 
of variation, based upon a larger series, would probably result 
in the separate recognition of this Perodipus. 
The measurements of my three examples are: 
No. Sex Total length Tail vertebrie Hind foot 
1552 9 296 175 41 
1553 2 284 181 43 
1539 fo) 281 167 2 
