_Remarks._--_Cratogeomys castanops excelsus_ lives in the deep soils of the arid interior basin of southwestern Coahuila and adjacent parts of Durango. This animal is common in the cultivated areas in, and in the vicinity of, the formerly extensive Laguna de Mayrán. East of this laguna the land becomes progressively higher, and _C. c. subsimus_ occurs in the higher, more dissected part of this area. _Specimens examined._--Total, 33, from: 8 mi. E and 2 mi. S Americanos, 3500 ft., 3; 4 mi. N Acatita, 3600 ft., 9; 20 mi. S El Hundido, 1; San Pedro, 2 (BSC); _1 mi. SW San Pedro de las Colonias, 3700 ft._, 4; 10 mi. N and 11 mi. W San Lorenzo, 2; 2 mi. E Torreón, 12. +Cratogeomys castanops subsimus+ Nelson and Goldman 1934. _Cratogeomys castanops subsimus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:144, June 13, type from Jaral, Coahuila. _Distribution._--Desert plains and lower foothills of mountains in south-central Coahuila (see fig. 1). _Comparisons._--From _Cratogeomys castanops goldmani_, found to the southwest, _subsimus_ differs in: Body larger; hind foot larger; upper parts paler, more yellowish and less rufous; skull larger and rougher, having more prominent ridges and crests and deeper fossae for attachment of muscles; zygomata more widely flaring; palate longer; rostrum broader; nasals longer; squamosal breadth greater; maxillary teeth larger. From _C. c. subnubilus_, found to the south, _subsimus_ differs in: Body larger; tail and hind foot shorter; upper parts paler, more yellowish-buff and less blackish; skull decidedly larger in all respects. From _C. c. planifrons_, found at higher elevations to the southeast, _subsimus_ differs in the same respects as _subsimus_ differs from _subnubilus_. For comparisons between _subsimus_ and subspecies to the west, north and northeast, see accounts above. TABLE 1. ~Measurements of Adult Female Cratogeomys from Coahuila, México~ Table legend: Column A: No. av. or cat. no. Column B: Total length Column C: Length of tail Column D: Length of hind foot Column E: Condylobasal breadth Column F: Zygomatic breadth Column G: Length of palate Column H: Breadth of rostrum Column I: Length of nasals Column J: Squamosal breadth Column K: Alveolar length of maxillary tooth-row ======================================================================== A B C D E F G H I J K ------------------------------------------------------------------------ _C. c. convexus_, Villa Acuña 52259 260 86 37 50.6 31.7 33.8 11.7 16.7 29.1 9.3 52261 265 83 38 49.3 31.6 32.9 11.8 15.8 28.9 10.6