JESimpson, 1938 Reithrodonomys 650+ft., 11.3mi. W. Hermosillo, Sonora. May 1, 1938. O>260 and F261,262 taken on level, tan, sandy soil with sparse dry grass among palo verde, palo fierro, and mesquite trees. The species of these mice is not known ; Dr.Benson suspects these as new species. 270+ft., Rancho de Costa Rica,Rio Sonora, Sonora. May 2,1938. Seven in mouse-traps and three in live- traps (O>270-74 ; F275,276) taken in wheat-field - bordered by corn field and mesquite. Dr.Benson suspects these harvest-mice as a new species. They are prob- able the same as the three (O>260 and F261,262) mentioned above from 11.3 mi. W. Hermosillo. May 3,1938 Fifteen taken in mousetraps (6O>and 3O>) and live-traps in wheat and corn fields(not saved).