Quast 1948 2 Perognathus arenaeius June 8 Punta Lasparino, 10-ft, 23°16'N, 110°9'W, Baja California 7♂, 6♀ (#325-337incl) caught last night in 48 live traps set among short dense shrubs on crest of sand dunes nearest the beach. Traps were baited with Sudan-grass seed and ran from camp southwest. This is the only species of mouse caught in these dunes in two days of trapping. Most of the mice were caught around the areas of short, densely matted bushes, the population seeming to drop off in areas less densely vegetated. Saw a large rattlesnake in one of the brush clumps two nights ago at dusk. Number 337 was the only female containing embryos, having 4 of 4 mm each. June 19 San Jorge 5-ft, 25°44'N, 112°07'W, Baja California 7♂, 4♀ (377-387incl) caught in Museum Special traps set last night in "Mangle Dulce" clumps along sand cliffs bordering estero north of camp. The "Mangle Dulce" grows next to the Mangrove of the estero but usually separated from it by at least the debris of high water mark, and usually a small strip of sand below the cliffs. Most of the traps were set on the top of the cliff within 10 feet of the edge, but a few set at the bottom of the cliff in sand but near the Mangroves also caught this species. Near the "Mangle Dulce" brushes large areas of crawling cactus were found and a