JESimpson 1938. 60. 100ft, 1mi. n. Puerto Libertad, Sonora. April 27, 1938, continued. The apparent scarcity of rodents here is probably accountable to the substrate rather than the vegetation which is much the same as many other more fruitful trapping areas. The granite of the hill does not lend itself readily to burrowing; there are few crevices tho numerous small caves suitably for woodrats (tho only two houses seen.) The zero catch in the livetraps I can not explain nor approach explanation; for the vegetation is heavy enough for cover and food, and the soil burrowed and burrowable. I am not satisfied as to the effectiveness of this type of live-trap: tin-box 2"x2"x6" with for- ward-dropping door set off from floor-treadle: [illegible] mouse steps on treadle(3) releasing the trigger(1) which is holding front-door (5) open, and front-door falls closed with safety-lever(2) falling in behind to hold door; to facilitate the removal of mice the rear of box also has a door(4). Put up mice and broke camp; drove thru the fishing village(after having lunch and fishing while writing notes; Senor Delgadillo and I each caught a halibut.) and around the bay to opposite headland and made camp!