Specimens of _pallidus_ from the desert slope of the San Gabriels are grayer (less brown) than specimens taken farther southeast in the Mojave and Colorado deserts. Further sampling of populations of _Perognathus fallax_ from areas adjacent to the San Gabriels might demonstrate differences of sufficient magnitude to warrant subspecific distinction of the San Gabriel population. Possibly, however, the San Gabriel series manifests only local variation in the race _pallidus_. Grinnell (1933:54) characterizes the ecological niche of the race _pallidus_ as being "open, sandy ground, often ... surrounded by rocky slopes," whereas these pocket mice in the San Gabriels inhabited gravelly or rocky juniper-dotted benches. _Specimens examined._--Total, 11, distributed as follows: Los Angeles County: 5 mi. E and 4 mi. S Llano, 4500 ft., 7; 2 mi. E Valyermo, 4500 ft., 3; 4 mi. E Valyermo, 5000 ft., 1. =Perognathus californicus dispar= Osgood California Pocket Mouse Mice of this subspecies were recorded from the lower chaparral association below about 4000 feet elevation along the coastal face of the San Gabriel Range. They were trapped on greasewood-covered slopes, in mixed growths of white sage and buckwheat, and beneath scrub oak and lilac chaparral; however none was taken in the heavy chaparral of the upper parts of the chaparral association. One small juvenile in gray pelage was taken in San Antonio Canyon on October 1, 1951. _Specimens examined._--Total, 5, distributed as follows: San Bernardino County: Lytle Canyon, 4000 ft., 2 (PC). Los Angeles County: San Antonio Canyon, 3000 ft., 3. =Perognathus californicus bernardinus= Benson California Pocket Mouse On Blue Ridge these mice were recorded between 7100 and 8000 feet elevation. Here they were restricted to dense tracts of snowbrush and sagebrush, often where these tracts were interspersed with, or beneath, open groves of conifers. These mice seemed to favor areas where this thick brush was broken by patches of open, grass-covered ground. Benson (1930:450) records this subspecies from Swarthout Valley, near Big Pines, at 6860 feet elevation. While setting traps for pocket gophers one mile southwest of Big Pines, in September of 1951, I frightened a pocket mouse from its burrow. The animal jumped into the tangle of interlacing twigs of a nearby clump of snowbrush, and with great dexterity climbed into the center of the bush, where it was lost to view. I was surprised at the facility with which this saltatorial rodent traveled through the network of small branches. In winter, in areas inhabited by this mouse, snow covers the ground for long periods during which these mice are probably forced to remain below ground. _Specimens examined._--Los Angeles County: 1 mi. S and 2 mi. W Big Pines, 7400 ft., 2. =Dipodomys panamintinus mohavensis= (Grinnell) Panamint Kangaroo Rat