No specimen of this subspecies has been examined. Jones and Anderson (1958:447) reported specimens from Rancho Pano Ayuctle as _R. f. intermedius_, but here those same specimens are assigned to _R. f. tropicalis_. J. A. Allen (1891:223) recorded specimens from Santa Teresa as _Ochetodon mexicanus_. According to Hooper (1952:142) that name was used by Allen for _R. fulvescens_. Allen's specimens from Santa Teresa are here referred to _R. f. intermedius_ on geographic grounds. _Records_ (Hooper, 1952:108): Camargo, 200 ft.; 20 mi. S Reynosa, Charco Escondido; Matamoros, 30 ft.; 7.5 mi. S Matamoros; 29 mi. S Cd. Victoria, 800 ft.; Hacienda Santa Engracia, 800 ft.; Santa Teresa (50 mi. SW Matamoros); Sierra San Carlos (El Mulato, Tamaulipeca, 1500 ft.). =Reithrodontomys fulvescens tropicalis= Davis 1944. _Reithrodontomys fulvescens tropicalis_ Davis, Jour. Mamm., 25:393, December 12, type from Boca del Río, 8 km. S city of Veracruz, Veracruz. _Distribution in Tamaulipas._--Tropical area in southeastern part of state. Most of the specimens examined of _R. fulvescens_ are included in this subspecies, principally because of their reddish coloration that is characteristic of _R. f. tropicalis_. According to the original description by Davis (1944:393) this subspecies is smaller than _griseoflavus_ and the posterior border of the incisive foramina terminate anterior to the plane of the molars. But, these characteristics are not found in any specimen examined from Tamaulipas and the average of external measurements is more than those given by Hooper (1952:109) for _tropicalis_. Of all specimens from Tamaulipas, those from the vicinity of Altamira and Tampico are most nearly typical of _tropicalis_. Weights of seven males and five females, from the Sierra de Tamaulipas, were, respectively, 13 (11-15), and 11 (9-14) grams. _Records of occurrence._--Specimens examined, 51: Rancho Santa Rosa, 25 km. N, 13 km. W Cd. Victoria, 1; Cd. Victoria, 3; Sierra de Tamaulipas, 10 mi. W, 2 mi. S Piedra, 1200 ft., 12; 2 km. W El Carrizo, 1; Ejido Santa Isabel, 2 km. W Pan-American Highway, 2000 ft., 14; Rancho Pano Ayuctle, 25 mi. N, 3 km. W El Mante, 300 ft., 4; Rancho Pano Ayuctle, 6 mi. N Gómez Farías, 300 ft., 4; 6 mi. N, 6 mi. W Altamira, 2; 1 mi. S Altamira, 3; 16 km. N Tampico, 3; 7 km. N Tampico, 4. Additional records: Hidalgo (Hooper, 1952:110); 5 mi. NE Gómez Farías, 1100 ft. (_ibid._); La Azteca, 5 km. NNE Gómez Farías (Goodwin, 1954:11); Gómez Farías (_ibid._); Antiguo Morelos (Hooper, 1952:110); 2 mi. W Tampico (Ingles, 1959:396). =Reithrodontomys mexicanus mexicanus= (Saussure) Mexican Harvest Mouse