Simpson, 1938 52. 900 ft., 1.6 mi. sw Las Alesnas, 20 mi. wsw Caborca, Sonora: April 18, 1938 Caught 1 Perognathus pencillatus (o>186), 1 Onychomys torridus (f 187; noemb.), 15 Dipodomys merriami (5 o>s put up: 188, 189, 190, 191, 192; Dr. Benson put up 5 f's from the party catch of 48 kangaroo rats: f 30 o>; 18 f; cheek- pouch contents saved). Set 50 mousetraps along same trapline as last night (on theory of having trapped-out most of the less desirable species) and 50 live-traps across wash in sand and creosote. April 19, 1938. Caught on second run mousetrap-line 4 Perognathus pencillatus (o> 198, 199; f 200, 201; cheek-pouch contents saved) and 6 Dipodomys merriami (4 o> and 2 f); in live-traps 1 Perognathus longi- membris (o> 194; in open space of creosote in sand) and 6 Pero- gnathus pencillatus (o> 195, 196, 197; 3 o>s turned loose; cheek-pouch contents saved). Shot a lizard in the sand (202). Broke camp and drove on, after having been given some good water from a 158 ft. deep well at Rancho Las Alesnas, into the pass, Puerto Blanco, and made camp at: 950 ft., 5 mi. sw Las Alesnas, 23 mi. wsw Caborca, Sonora. April 19, 1938, continued. Went 1/2 mi. nw. of camp to granite (rotten) and quartz hill and set 50 mousetraps and 7 rat-traps among creosote, torote, ocotillo, saquaro, cardon (in bloom), cholla, white succulents, and small cacti.