Simpson, 1938 50+ ft., Cerro La Cholla, 6 mi. wnw Punta Peñasca, Sonora April 6, 1938, continued. After putting specimens and repairing traps we broke camp and returned to Punta Peñasca where we bought water and half-dried fish. Drove over the sand (getting stuck a few times) to: 100+ ft., Cerro Prieto, 6 mi. nw Punta Peñasca, Sonora. Here we made camp on the sand among the dark lava rocks of which the hill is composed. Ocotillo and cholla are the dominate plants Set out 50 mousetraps and 17 rat traps on the rock-hill; a few of the mousetraps trailing off into the sand bordering the base of the hill. April 7, 1938 Caught 3 Peromyscus eremicus (♀131, ♀132, ♂133), 3 Neotoma lepida (♂134, ♂135, ♀136), and 4 Dipodomys merriami (3♂'s; 1♀ [illegible]); the latter were not put up, but cheek-pouch contents saved. Saw a Great Horned Owl on the hill at dawn when on trap-line without my shot-gun; the owl allowed me to approach within 30 yards before leaving perch. After putting up specimens (Dr. Benson helped me) I went back for the owl but failed to find it; shot aniguana [= chucha walla by Mexicans] in the dark rocks at edge of the sand and saw a second dart into a kangaroo-rat hole under a creosote-like bush which was 50-60ft. from the rocks out in the soft sand. After lunch we broke camp and drove back 45.