_Records of occurrence._--Specimens examined, 121: 7 km. S, 2 km. W San Fernando, 7; 7 km. SW La Purisima, 1; Rancho Santa Rosa, 25 km. N, 13 km. W Cd. Victoria, 260 m., 2; 36 km. N, 10 km. W Cd. Victoria, 1; 15 mi. N Cd. Victoria, 2; 4 mi. N La Pesca, 5; Soto la Marina, 25; Sierra Madre Oriental, 5 mi. S, 3 mi. W Cd. Victoria, 1900 ft., 18; Sierra de Tamaulipas, 2 mi. S, 10 mi. W Piedra, 1200 ft., 36; Sierra de Tamaulipas, 3 mi. S, 10 mi. W Piedra, 1200 ft., 1; Ejido Santa Isabel, 2 km. W Pan-American Highway, 2000 ft., 3; Rancho Pano Ayuctle, 25 mi. N, 3 km. W El Mante, 300 ft., 1; Rancho Pano Ayuctle, 6 mi. N Gómez Farías, 300 ft., 8; 10 km. N, 8 km. W El Encino, 400 ft., 1; 2 km. W El Carrizo, 6; 53 km. N El Limón, 4; 8 km. NE Antiguo Morelos, 2; Altamira, 1; 1 mi. S Altamira, 3; 10 mi. NW Tampico, 1; 7 km. N Tampico, 2. Additional records: Hidalgo (Goldman, 1911:59); Matamoros (_ibid._); Bagdad (_ibid._); Sierra de San Carlos (Hooper and Handley, 1948:20); 3 mi. W Soto la Marina (Hooper, 1953:5); [Cd.] Victoria (Goldman, 1911: 59); Acuña (Hooper and Handley, 1948:20); Mesa de Llera (Hooper, 1953:5); Gómez Farías (Goodwin, 1954:9); 2 mi. S Cd. Mante (Ingles, 1959:394); Antiguo Morelos (Hooper and Handley, 1948:20). =Castor canadensis mexicanus= V. Bailey Beaver 1913. _Castor canadensis mexicanus_ V. Bailey, Proc. Biol. Soc. Washington, 26:191, October 23, type from Ruidoso Creek, 6 mi. below Ruidoso, Lincoln Co., New Mexico. _Distribution in Tamaulipas._--Probably in the Río Grande drainage. The beaver has been reported in Tamaulipas only from Matamoros (Baird, 1858:355--three specimens) and from 12 miles below, south of, Matamoros (V. Bailey, 1905:124). In Tamaulipas the beaver may occur only in the Río Grande drainage. =Oryzomys palustris= Marsh Rice Rat Previous to this report only one subspecies of _Oryzomys palustris_ had been recorded from Tamaulipas. Careful examination of the available material from the state shows that _O. p. aquaticus_ occurs in the east and _O. p. peragrus_ lives in the southwestern part of the state. In general, specimens examined were trapped in dense brush alongside waterholes as at Altamira, or around cornfields as at the place 36 kilometers north and 10 kilometers west of Ciudad Victoria, where the bushes were mesquite and other kinds of Acacias. There the ground was covered by cat claw, and no grass was seen near the traps in which _O. palustris_ was caught. In the Sierra de Tamaulipas a specimen was caught among rocks and bushes. Ingles (1959:395) reported that his specimens were trapped alive in dense brush and "tules." A female taken at Jaumave on July 25 had 5 embryos, each 20 mm. in crown-rump length. =Oryzomys palustris aquaticus= J. A. Allen