Additional records (Osgood, 1909:131, unless otherwise noted): Nuevo Laredo; Mier; Camargo; near Bagdad; Sierra San Carlos (Hooper, 1953:7); Matamoros-Victoria Highway (_ibid._); Charco Escondido (Baird, 1858:464); Hidalgo; Cd. Victoria; 10 mi. NE Zamorina (Hooper, 1953:7); Gómez Farías (Goodwin, 1954:12); Chamal (_ibid._); Tula (Hooper, 1953:7); Antiguo Morelos (_ibid._); Altamira (Goldman, 1942:158); 2 mi. W Tampico (Ingles, 1959:397); Tampico. =Peromyscus boylii= Brush Mouse 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 León. _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 Acuña (_ibid._); Rancho Viejo (Goodwin, 1954:12); Santa María (_ibid._); Joya de Salas (_ibid._). =Peromyscus pectoralis= White-ankled Mouse