This subspecies is easily distinguished from _L. i. texensis_ by the following features: hind foot larger, 31.5 (30-33.5) instead of 27.8 (27-29); skull longer, 34.2 (32.4-36.4) instead of 31.5 (30.0-32.5); maxillary tooth-row longer, 5.4 (5.0-5.8) instead of 5.0 (4.8-5.1); interorbital constriction relatively narrower in _alleni_. Intergradation between _L. i. alleni_ and _L. i. texensis_ takes place at Rancho Santa Rosa (where, of the two specimens, one is conspicuously larger than the other), eight kilometers northeast of Antiguo Morelos, El Encino, and Ejido Santa Isabel. All specimens from the localities mentioned are here assigned to _texensis_. Weight of three pregnant females averaged 68.9 (64-78) grams, that of non-pregnant females, 65.6 (64-68), and that of six males 73.0 (65-80). _Records of occurrence._--Specimens examined, 34: Villa Mainero, 1700 ft., 2; Nicolás, 56 km. NW Tula, 5500 ft., 6; Jaumave, 2400 ft., 23; 16 mi. N, 6 mi. W Palmillas, 5500 ft., 1; 14 mi. N, 6 mi. W Palmillas, 5500 ft., 2. Additional records: Miquihuana (Goldman, 1911:56); Tula (Hooper and Handley, 1958:18). =Liomys irroratus texensis= Merriam 1902. _Liomys texensis_ Merriam, Proc. Biol. Soc. Washington, 15:44, March 5, type from Brownsville, Cameron Co., Texas. 1911. _Liomys irroratus texensis_, Goldman, N. Amer. Fauna, 34:59, September 7. _Distribution in Tamaulipas._--State-wide except extreme southwestern and northwestern parts. Intergradation occurs between _L. i. texensis_ and _L. i. pretiosus_ in southeastern Tamaulipas as noted previously by Hooper (1953:5). Individuals from Altamira and one mile south thereof are small and dark as in _pretiosus_, but cranial measurements are as in _texensis_ to which they are here assigned. Specimens from the vicinity of Tampico are typical _texensis_. Average weight of the specimens from three different localities are as follows: Soto la Marina, seven males, 42.7, 14 females, 36.9; Sierra de Tamaulipas, 12 males, 47.3, 20 females, 40.7; Sierra Madre Oriental, eight males, 45.5, nine females, 37.0 grams. The specimens reported by Ingles (1959:394) from two miles south of El Mante as _L. irroratus_ are here referred to _texensis_ on geographic grounds.