_Remarks._--_Cratogeomys castanops subsimus_ is the largest known subspecies of the species in cranial dimensions, but is exceeded in size of body by _C. c. jucundus_ to the north. Of adjacent subspecies, _subsimus_ is the most closely related to _excelsus_ and shows little or no relationship to the smaller and darker _C. c. subnubilus_ and _C. c. planifrons_, which are found at higher elevations to the south and southeast, respectively. Movements by _subsimus_ to the north, east, and south are barred by inhospitable mountains. Specimens of _subsimus_ from the northeastern part of its range are larger and darker than other specimens assigned to this subspecies. An adult female, assigned to _subsimus_, from the vicinity of Santa Rosa is noticeably smaller and paler than typical specimens of this subspecies. _Cratogeomys castanops subsimus_ occurs in scattered colonies in sandy soils principally in the upper drainage of the Río Salinas. Specimens have also been taken from the foothills of the Sierra Madre Oriental and westward on the elevated desert plains. _Specimens examined._--Total, 22, from: 3 mi. S and 3 mi. E Muralla, 3800 ft., 3; 2 mi. N Santa Cruz, 2; 21 mi. S and 11 mi. E Australia, 4400 ft., 6; Jaral, 3860 ft., 4 (BSC); _Hacienda El Tulillo, 5 km. S Hipolito_, 2; 17 mi. N and 8 mi. W Saltillo, 5200 ft., 1; 3 mi. N and 5 mi. W La Rosa, 3600 ft., 1; 12 mi. N and 10 mi. E Parras, 5000 ft., 1; N foot Sierra Guadalupe, 9 mi. S and 5 mi. W General Cepeda, 6200 ft., 1; _N foot Sierra Guadalupe, 10 mi. S and 5 mi. W General Cepeda, 6500 ft._, 1. +Cratogeomys castanops goldmani+ Merriam 1895. _Cratogeomys castanops goldmani_ Merriam, N. Amer. Fauna 8:160, January 31, type from Cañitas, Zacatecas. _Distribution._--Plains of northeastern Zacatecas, northward into extreme southwestern Coahuila (see fig. 1). _Comparisons._--Compared with _Cratogeomys castanops subnubilus_, found to the east, _goldmani_ differs in: Body larger, tail and hind foot longer; color paler, more rufous and less blackish; skull larger; zygomata more widely flaring; palate larger; rostrum broader; nasals longer; maxillary teeth larger. Compared with _Cratogeomys castanops rubellus_ Nelson and Goldman, found to the southeast, _goldmani_ differs in: Body and skull smaller; zygomata less widely flaring; palate shorter; rostrum narrower; maxillary teeth smaller. _Remarks._--Records of _goldmani_ given here extend the known range of this subspecies northward into southwestern Coahuila. Specimens assigned to this subspecies from Coahuila compare favorably with topotypes of _goldmani_ (see tables 1 and 2) but are slightly paler, and in this respect show some relationship to _excelsus_. The ranges of these two subspecies however, are partly isolated by mountainous country in southern Coahuila. _Specimens examined._--Total, 6, from: W foot Pico de Jimulco, 4600 ft., 1; _Valley Río Aguanaval, 1 mi. S Jimulco_, 4; 1-1/2 mi. N Parras, 1.