C.V. Miller 1940 Peromyscus boylii March 20 5800' +/- 1/2 mi. N Mt. Emory, Chisos Mts., Brewster Co., Texas. Set out 50 mouse traps about 10 PM in moonlight on W facing slope. Rocky-small loose rocks, with growth of Mesquite, small yucca, and other brush, medium thick. Caught one immature P. boylii. March 28 2900'+ elevation. La Calera, 2 mi. S W of Santa Catarina, Nuevo Leon, Mexico. Desert, mountainous country, low-medium thick brush, rocky, cacti abundant. P. boylii was the only mammal caught in 2 nights of trapping on the^a mountain, although S.B. Benson got Perognathus in the valley below. March 31 2400+ ft. Rancho Rodeo, 7.3 mi. S Santa Catarina, Nuevo Leon. On March 30 I took 3 P. boylii, 1 ?, 2 ? in mouse traps baited with oatmeal. These traps were set along a brush fence by a wheat field. On March 31 I took 7 of the same 4?, 3 ?, in traps set on a rocky, brush and cactus covered hill. May 6 El Pedregal, 2.5 mi. W Tlalpan, D.F. (Mexico) Took 9?, 8 ? & this species both on grassy hill and among lava rocks, the latter having a growth of grass, oaks, Nopal cactus, etc. May 12 El Roble, 8 mi. NE Tepotitlan de Morelos, Jalisco. Took 2 ? & 2 of this species in small dry brush near large oak trees. Grass (dry) and rocks also present. May 18 6 mi. SE Punta, Jalisco. Took one ? with 2 embryos in a trap set among small rocks, dry grass and brush at the base of a rock cliff.