Boulevard, ST 1942 Reithrodontomys Apr. 2 Beglund Ranch, 1450 ft., 5 mi. N Corralitos, Santa Cruz Co., Calif. One taken in a line of 146 Museum Special traps set two nights on a north facing hillside along the edge of chaparral consisting largely of Baccharis with some poison oak, Ceanothus, Lotus sp. Chaparral a closed stand where this specimen was taken with practically no cover to the sandy soil. This specimen a female with no embryos. Apr. 7 Muddy Creek, 1000 ft., 1 mi. S Chualar Canyon, Monterey Co., Calif. Two male specimens were taken in a line of 37 Museum Special traps set in a stand of Artemisia californica with some Salvia mellifera, Baccharis sp, and short grass. Apr. 8 Seven were caught in a line of 127 traps set in the same habitat as described above. There are numerous small runs of these mice threading the short grass. Four of the animals caught are male and three female. None of the females had embryos. Apr. 9 Nineteen of these mice were trapped, again along the wood road on the flat in shoulder-high growth composed mainly of Artemisia californica. These little mice seem by far the dominant animal, or anyway most numerous small mammal, of this habitat. Of these 13 are males and 6 are females. None of the females possess embryos, an indication, it would seem, that this is not the breeding season. The fact that a larger number was caught last night than the night before when 127 traps were set in the same habitat