JESimpson, 1938. 2550+ft, lava bed, 19 mi. SE Moctezuma, Sonora. May 25, 1938. Caught on dark lava hill-side in dense brush one Peromyscus eremicus (not saved) and 1 Perognathus gold- mani (?431); on lava hill-top in light brush one juvenile Perognathus baileyi (?7433, v); on tan rocks near lava hill 2 Perognathus penicillatus (?7434, ?7435, ?436, ?437), one Perognathus baileyi (?7432), and one Peromyscus eremicus (not saved). Broke camp and drove 8.4 miles to Rancho Garumbullo where we bathed and then drove 10.9 miles to Moctezuma where we picked up mail and supplies. Drove down dry- bed of Rio Moctezuma to: 2300+ft, 1 mi. S. Moctezuma, Sonora. May 25, 1938, continued. camp Made beside wheat-field and few hundred yards from dark lava hill where set 10 rat-traps and 43 mouse- traps in rocks and brush and then after dark 50 live-traps in wheatfield. May 26, 1938. Caught on lava hill 2 Perognathus goldmani (?7438, ?7439) and 6 Peromyscus eremicus (?7440, ?7441); in live-trap in wheat-field one Perognathus penicillatus (?7442). Catalogued a lizard (?443) brought in for pay (5-10 centavos) by Mexican boy, one of several hired 2 years ago by Dr. Benson to hunt lizards and frogs. Set 9 gopher traps in wheatfield and melon- patch. Caught one juvenile Thomomys umbraeus :