E.V. Miller 1940 Peromyscus leucopus March 24 400'± elev. 38 mi. S Nuevo Laredo in Nuevo Leon, Mexico. Took two immatures in mouse traps baited with oatmeal and birdseed, and set on rocky ground in open brush, flat country, considerable cactus. March 30 2400' ft. Rarcho Rodeo, 7.3 mi. S Santa Catarina, Nuevo Leon. Took 1 ♀ immature P. leucopus in mouse traps set by a brush fence near a wheat field. April 6 Elevation about 100 ft. 24 mi. ESE Reynosa, Nuevo Leon, Mexico. Took one ♂ in mouse trap set in habitat of large mesquite trees and prickly pear cactus; also other species of brush and cactus. Fairly open. April 11 Charco Escandido, 20± mi. S Reynosa, Tamaulipas. Took 2 ♂s of this species, one young, near the pond, near thick mesquite and other brush. Fine gray-brown, sandy soil. On April 12 I took more of this species. They appeared to live where the mesquite was thickest, while the other abundant rodent of this region, Perognathus merriami, lived in more open places. April 14 36 mi ESE Monterrey, Nuevo Leon. Took 1 ♂, 1 ♀ on slightly rocky ground near low hill covered with medium growth of thorny brush. April 17 Km 755, Cruz y Cruz, 29 mi. N Ciudad Victoria, Tamaulipas. Took 3 ♀, 1 ♂ in mouse traps set along a cornfield next to brush. April 18 Arroyo los Miradores, 1 mi. W Km. 619, 22 mi. N Pimón, Tamaulipas. Took 4 ♂, ♀ in tropical habitat - dense brush - large trees.