+Cratogeomys castanops subnubilus+ Nelson and Goldman 1934. _Cratogeomys castanops subnubilus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:145, June 13, type from Carneros, 6800 ft., Coahuila. _Distribution._--Intermontane valleys and plains of southeastern Coahuila and probably adjacent parts of Zacatecas, San Luis Potosí and Nuevo León (see fig. 1). _Comparisons._--_Cratogeomys castanops subnubilus_ needs close comparison only with _Cratogeomys castanops planifrons_, found to the east and from which _subnubilus_ differs in: Body, hind foot and skull smaller; upper parts, in summer pelage, paler, more rufous-buff and less dark russet; underparts paler, more whitish and less blackish; hairs of hind foot reddish rather than blackish; zygomata more widely flaring; palate shorter, especially in females; rostrum broader, especially in females; nasals slightly smaller; squamosal breadth greater; incisors narrower, especially in males; maxillary teeth smaller. From _Cratogeomys castanops rubellus_ Nelson and Goldman, found to the south in San Luis Potosí, _subnubilus_ differs in: Body, hind foot and all parts of skull smaller; upper parts and underparts darker, more blackish and less rufous. _Remarks._--_Cratogeomys castanops subnubilus_ is the smallest subspecies of _C. castanops_ (see tables 1 and 2). This subspecies is dark and lives at high elevations (5500 ft. to 6800 ft.) in deep valley soils in relatively isolated intermontane valleys and elevated plains. It is differentiated to a much higher degree from adjacent subspecies of _C. castanops_ than is usual in this species, and no intergrades between _subnubilus_ and other subspecies have been taken. In the Sierra Guadalupe, _subnubilus_ was trapped at 6700 feet within twomiles of a place where _subsimus_ was taken at 6500 feet. _Specimens examined._--Total, 31, from: 1 mi. N Agua Nueva, 5500 ft., 1; Domingo Cañon, Sierra Guadalupe, 6700 ft., 11 mi. S and 4 mi. W General Cepeda, 1; Carneros, 6800 ft., 6 (BSC); _1 mi. S Carneros, 6000 ft._, 4; 2 mi. W San Miguel, 5500 ft., 3; 8 mi. N La Ventura, 6000 ft., 10; La Ventura, 5600 ft, 6 (BSC). +Cratogeomys castanops planifrons+ Nelson and Goldman 1934. _Cratogeomys castanops planifrons_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:146, June 13, type from Miquihuana, 5000 ft., Tamaulipas (listed, by mistake, as southern Nuevo León). _Distribution._--Elevated montane valleys of Sierra Madre Oriental of extreme southeastern Coahuila, south and east into southwestern Nuevo León and Western Tamaulipas (see fig. 1).