1945. _Oryzomys fulvescens engracie_ Osgood, Jour. Mamm., 26:300, November 14, type from Hacienda Santa Engracia (32 km. N), NW of Cd. Victoria, Tamaulipas. _Distribution in Tamaulipas._--Central and southeast parts of state. _Records of occurrence._--Specimens examined, 13: 2 km. W El Carrizo, 5; Rancho Pano Ayuctle, 25 mi. N, 3 km. W El Mante, 6; 10 km. N, 8 km. W El Encino, 1; 7 km. N Tampico, 1. Additional record: Altamira (Osgood, 1945:300). =Reithrodontomys megalotis hooperi= Goodwin Western Harvest Mouse 1954. _Reithrodontomys megalotis hooperi_ Goodwin, Amer. Mus. Novit., 1660:1, May 25, type from Rancho del Cielo, 5 mi. NW Gómez Farías, 3500 ft., Tamaulipas. _Distribution in Tamaulipas._--Known only from type locality. =Reithrodontomys fulvescens= Fulvous Harvest Mouse This is the most common species of _Reithrodontomys_ in Tamaulipas; it occurs in almost all parts of the state, from sea level to high up in the mountains and from the tropical forest to the desert plain. The three subspecies in the state are _R. f. intermedias_ in the northern half, _R. f. griseoflavus_ in the high parts of the Sierra Madre Oriental, and _R. f. tropicalis_ in the southeast. The lines between these subspecies are difficult to establish because the zones of intergradation are broad. Characters for separating the three subspecies in Tamaulipas are listed by Hooper (1952). =Reithrodontomys fulvescens griseoflavus= Merriam 1901. _Reithrodontomys griseoflavus_ Merriam, Proc. Washington Acad. Sci., 3:553, November 29, type from Ameca, 4000 ft., Jalisco. 1952. _Reithrodontomys fulvescens griseoflavus_, Hooper, Miscl. Publ. Mus. Zool., Univ. Michigan, 77:98, January 16. _Distribution in Tamaulipas._--Known only from Jaumave. Only specimens from Jaumave are clearly _R. f. griseoflavus_; all others east of this locality are intergrades between _griseoflavus_ and _tropicalis_, under which latter subspecies they are included. In _griseoflavus_ the tail is longer in relation to the head and body, 141.2 (135-153) per cent, than in the other two subspecies that occur in Tamaulipas. The average weight of 14 males was 14 (12-16) grams. _Record of occurrence._--Specimens examined, 15, from Jaumave, 2400 ft. =Reithrodontomys fulvescens intermedius= J. A. Allen 1895. _Reithrodontomys mexicanus intermedius_ J. A. Allen, Bull. Amer. Mus. Nat. Hist., 7:136, May 21, type from Brownsville, Cameron Co., Texas. 1914. _Reithrodontomys fulvescens intermedius_, A. H. Howell, N. Amer. Fauna, 36:47, June 5. _Distribution in Tamaulipas._--Northern half of state.