Specimens examined were obtained at higher elevations in the oak-tree
zone of the Sierras in traps set among rocks, trees and in grassy
areas. _Peromyscus boylii_ was trapped in the same area as was _P.
pectoralis_ and no habitat distinction between the two was noted. Some
behavioral differences, however, are pointed out in the account of _P.
pectoralis_. Morphological differences between these two species in
Tamaulipas were reported by Hooper (1952:372).
A female taken on August 5 in the Sierra Madre Oriental carried two
embryos 15 mm. in crown-rump length.
For the taxonomic status of _P. boylii_ in Tamaulipas see Alvarez
(1961).
=Peromyscus boylii ambiguus= Alvarez
1961. _Peromyscus boylii ambiguus_ Alvarez, Univ. Kansas
Publ. Mus. Nat. Hist., 14:118, December 29, type from
Monterrey, Nuevo Leon.
_Distribution in Tamaulipas._--Known only from the Sierra
San Carlos.
_Record of occurrence._--Specimens examined, 7 (UMMZ), all
from La Vegonia, Sierra San Carlos.
=Peromyscus boylii levipes= Merriam
1898. _Peromyscus levipes_ Merriam, Proc. Biol. Soc.
Washington, 12:123, April 30, type from Mt. Malinche, 8400
ft., Tlaxcala.
1909. _Peromyscus boylii levipes_, Osgood, N. Amer. Fauna,
28:153, April 17.
_Distribution in Tamaulipas._--Central and southern parts of
state.
Weights of 19 males and 18 females from the Sierra Madre Oriental are,
respectively, 25.2 (22-30) and 23.6 (20-29); weights of eight males and
five females from the Sierra de Tamaulipas are 24.9 (22-32) and 29.6
(24-31).
_Records of occurrence._--Specimens examined, 54: Sierra
Madre Oriental, 8 mi. S, 6 mi. W Victoria, 4000 ft., 37; 5
mi. S, 3 mi. W Victoria, 1900 ft., 2; Ejido Eslabones, 10
mi. W, 2 mi. S Piedra, 1200 ft., 1; Sierra de Tamaulipas, 11
mi. W, 8 mi. S Piedra, 2000 ft., 13; 2 km. W El Carrizo, 1.
Additional records: Rancho del Cielo (Hooper, 1953:7); 3 mi.
NW Acuna (_ibid._); Rancho Viejo (Goodwin, 1954:12); Santa
Maria (_ibid._); Joya de Salas (_ibid._).
=Peromyscus pectoralis=