I consider my series of _Peromyscus truei_ from the desert slope of the San Gabriels to represent the subspecies _montipinoris_. The series is closely comparable to specimens of the subspecies _montipinoris_ in the California Museum of Vertebrate Zoology from the Mount Pinos area, but differs from specimens of the race _chlorus_ from the San Bernardino Mountains in certain diagnostic characteristics. In his recent paper on _Peromyscus truei_, Hoffmeister (1951) considered the populations of this species in the San Gabriels to be of the race _chlorus_. Hoffmeister had only one specimen available from the San Gabriel Mountains (Lytle Creek, on the Pacific slope) which was intermediate between _montipinoris_ and _chlorus_, but on the basis of cranial measurements it was referred to the race _chlorus_. Specimens of _Peromyscus truei_ from the eastern end of the desert slope of the San Gabriel Mountains and the Cajon Pass area would probably demonstrate that the race _montipinoris_, which occupies the desert slope of the San Gabriels, intergrades with the race _chlorus_, which occurs in the San Bernardino Range immediately to the east, in the Cajon Pass area. Although _montipinoris_ occurs on the desert slope of the San Gabriels, _chlorus_ may occur on the Pacific slope. I took no specimens of the piñon mouse on the Pacific slope of the San Gabriel Mountains. In December, 1948, many small juveniles were taken in the juniper belt, and on October 15, 1951, two females trapped at the head of Grandview Canyon had embryos: one three and the other four. On November 13, 1951, a partially gray-pelaged subadult female was trapped which had recently suckled young. _Specimens examined._--Total, 17, all in Illinois Museum of Natural History, distributed as follows: Los Angeles County: Mescal Canyon, 4500 ft., 8 mi. SE Llano, 11; Mescal Canyon, 4300 ft., 2; 6 mi. SE Valyermo, 5100 ft., 1; Grandview Canyon, 6 mi. SE Valyermo, 5100 ft., 1. San Bernardino County: 1 mi. W Cajon, 3200 ft., 2. =Onychomys torridus pulcher= Elliot Southern Grasshopper Mouse Grasshopper mice seemed to be partial to the more sandy parts of the Joshua tree flats where the mice were trapped regularly but not abundantly. This mouse inhabited the barren sandy channels of Mescal Wash but was rare on the adjacent juniper-clad benches. In the arid, sandy washes this typical desert rodent penetrated the high pinyon-juniper association. Wherever grasshopper mice occurred they were outnumbered by most of the other rodent species. For example, on November 26, 1949, below Graham Canyon, 100 snap traps yielded 10 _Dipodomys panamintinus mohavensis_, 2 _Dipodomys merriami merriami_, 4 _Peromyscus maniculatus sonoriensis_, and 3 _Onychomys torridus pulcher_. Where abandoned kangaroo rat burrows were common in the Joshua tree belt these burrows were used as retreats by _Onychomys_. Some traps set at the entrances to old burrows caught grasshopper mice.