Palmer 1934 Peromyscus maniculatus Cottonwood Sgs., [mid] Old Woman Sgs., San Bernard- ino Co., Calif. Dec.29 Caught 1 P. m. sonorensis in 90 mouse traps which were set mainly on deep sand which had a scattered growth of Coriella, Atriplex, Chenopodium, Deer Cain Wash, 4 1/2 mi. NE Upland, 1550 ft., San Bernardino Co., Calif. Dec.31 Caught 1 in 57 gov size mouse traps set in washland rather thickly grown up with Salvia apiana, Adenostoma fasciculatum, Eriogonum fasciculatum, Artemisia and a few scattered clumps of Prunus ilicifolia and Cercocarpus reticulatfolias. Apparently Peromyscus frutes- ulus and this species are mutually exclusive here. This is the only place I have caught both in the same trapline. 3 mi. E Ontario, 1025 ft. San Bernardino Co. Calif. Dec.30 Examined traps set at 6 P.M at 10 P.M. and found 5 in 15 gov. size mouse traps set on sand dunes in an old vineyard. Dec.30 Dec.31 From 10 P.M. to 6 A.M. caught 5 in 12 mouse traps set on sand dunes. Apparently here, the mice are as active in late at night or early in the morning as they are in the evening.