JESimpson, 1938. 75. 650+ft., Sierra Serri, 9mi.w Rancho San Javier, 75mi.n Hermosillo, Son. May 10, 1938, continued. Set 50 mousetraps and 10 rat-traps (Schuylers) on rocky hill among torote, palo verde, creosote, ocotillo, and pitayo. May 11, 1938. Caught 12 Perognathus intermedius (5♂s and 7♀; (4) (5) (no) (no) (emb) → 345, 346 and ♀ 347, 348, 349, 350), 5 Perognathos baileyi (0♂2 and 3♀: ♂351, 352 and ♀353), and 4 Neotoma albigula (3♂s and a juvenile; ♂354, 355, 356). Broke camp late and drove toward Rancho Libertad, the type locality for Dipodomys deserti sonoriensis. By the bright moonlight hunted along road for mounds; how- ever we were unsuccessful even at R. Libertad, but, when, both by chance and foresight, we parked off road to sleep, we found the rat-holes less than 10 ft. from the truckat: 300+ft., (Rancho Dolores), 7 mi. ese Rancho Libertad, Sonora. Set out 10 Schuyler and 7 wooden rat-traps in sand at rat-holes (among mesquite trees). May 12, 1938. Caught 2 Perognathus penicillatus (no emb ♀357) and two Dipodomys deserti (♂358; no emb ♀359). Cheek-pouch contents saved. Broke camp and drove to Hermosillo where we picked-up mail, laundry, photographs, etc. A letter to Dr Benson from Mr. Powell, vice-consul and acting-consult at Nogales, gave the information that we must return to Nogales and cross the U.S.-Mexico line in order to clear properly