Quest 1948 Peromyscus maniculatus 2 June 21 San Jorge, 5+ ft, 25044'N, 11207'W, Baja California Three males (#417, 418, 419) and one immature male caught in Museum special traps baited with walnut and set at north end of estero last night. Traps were set in area bordered by "Mangle Dulce" on one side and a thick, stunted mangrove thicket on the other and on boggy ground full of crab burrows on which composite plants formed a sparse cover. The specimens were caught in traps set under the Mangroves and "Mangle Dulce" and the greater percentage of the traps set in the boggy open area between yielded nothing but several crab pinners. The line of "Mangle Dulce" bushes formed the dividing line between dry and boggy ground and the Peromyscus maniculatus were caught under them on the wet side while Perognathus arenarius were caught on the dry side in live traps only a few feet away. Dr. Benzen, Tevis and Murray have been consistently setting their Museum specials in and on top of the Mangroves in the thickets south and north of camp and have caught a great number of this species, the number caught dropping off very rapidly as the traps leave the mangroves. Although the mangroves are flooded by the high tides, it is evident that this species prefers and spends its entire time in the mangroves. In this area it is not to be