In studying Tamaulipan specimens, I was mindful that Hershkovitz (1951:550) regarded all opossums of this species in México as a single subspecies, even though J. A. Allen (1901) recognized two subspecies in the northeastern part of the Republic. According to Allen (p. 172), _D. m. texensis_ (to which he ascribed a distribution in Texas and adjoining Tamaulipas) was described as: "Similar in coloration to _D. marsupialis_ (_typica_) [_D. m. californica_], but with a relatively longer tail, longer nasals, usually terminating posteriorly in an acute angle, instead of being rounded or more or less abruptly truncated on the posterior border." The available material from Tamaulipas can be divided into two groups on the basis of shape and proportion of the nasals. In opossums from the southeast the nasals are truncate posteriorly and average 47.0 (45.1-48.4) per cent of the condylobasal length, whereas in specimens from elsewhere the nasals are acute posteriorly and average 50.7 (49.7-51.8) per cent of the condylobasal length. Tentatively, therefore, I follow Allen in recognizing two subspecies in northeastern México. I note no especial difference in length of tail between _texensis_ and _californica_. Hooper (1951:3) followed Hershkovitz in reporting as _californica_ a specimen from Rancho del Cielo; to me, specimens from this area are referable to _texensis_. One of the specimens from two miles south and 10 miles west of Piedra (54917) has a supernumerary tooth lingual and anterior to the last upper molar. The tooth is small (2.7 mm. long) and peglike. _Records of occurrence._--Specimens examined, 8: 3 mi. N Soto la Marina, 1; 2 mi. S, 10 mi. W Piedra, 12,000 ft., 7. Additional records: Matamoros (Baird, 1858:234); Altamira (J. A. Allen, 1901:167). =Didelphis marsupialis texensis= J. A. Allen 1901. _Didelphis marsupialis texensis_ J. A. Allen, Bull. Amer. Mus. Hist., 14:172, June 15, type from Brownsville, Cameron County, Texas. _Distribution in Tamaulipas._--Northern, central and southwestern parts of state. _Records of occurrence._--Specimens examined, 7: San Fernando, 180 ft., 1; Villa Mainero, 1700 ft., 2; 36 km. N, 10 km. W Cd. Victoria (1 km. E El Barretal), on Río Purificación, 1; 12 km. N, 4 km. W Cd. Victoria, 1; Ejido Santa Isabel (12 km. S Llera), 2 km. W Pan-American Highway, 2000 ft., 1; 4 mi. N Jaumave, 2500 ft., 1. Additional records: Matamoros (J. A. Allen, 1901:173); El Mulato, San Carlos Mts. (Dice, 1937:249); Rancho del Cielo (Hooper, 1953:3). =Philander opossum pallidus= (J. A. Allen) Four-eyed Opossum 1901. _Metachirus fuscogriseus pallidus_ J. A. Allen, Bull. Amer. Mus. Nat. Hist., 14:215, July 3, type from Orizaba, Veracruz. 1955. _Philander opossum pallidus_, Miller and Kellogg, Bull. U. S. Nat. Mus., 205:8, March 3.