_Type._--Female, adult, skin and skull, No. 34589, Univ. Kansas Mus. Nat. Hist., Don Martin, 800 ft., Coahuila; 19 August 1949; obtained by W. Kim Clark, original number 1034. _Distribution._--Extreme northeastern Coahuila from the vicinity of Presa Don Martin southward into northwestern Neuvo León in the valley of the Río Salado and its tributaries at least as far south as the vicinity of Vallecillo (see fig. 1). _Diagnosis._--Body large for species (see tables 1 and 2); hind foot short; upper parts Apricot Buff (in fresh summer pelage) and Salmon-Buff strongly mixed with black (in fresh winter pelage); underparts Light Ochraceous-Buff; skull large, especially in females, and broad; zygomatic arches widely flaring; palate long; rostrum broad; nasals long; mastoid and tympanic bullae not conspicuously inflated; incisors narrow; maxillary teeth large. _Comparisons._--From _Cratogeomys castanops bullatus_ found to the north, _ustulatus_ differs in: Body larger; tail shorter; upper parts darker, more rufous and less buffy; skull larger, especially in palate, nasals, and rostrum; zygomata more widely flaring; tympanic bullae less inflated; incisors slightly larger; maxillary teeth larger. From topotypes of _Cratogeomys castanops tamaulipensis_ found to the southeast, _ustulatus_ differs in: Body larger; upper parts, in winter pelage, darker, more rufous and less buffy; underparts paler; skull larger, especially in palate, rostrum and nasals; zygomata more widely flaring; tympanic bullae more inflated; pterygoids larger; basioccipital narrower, its sides parallel instead of convex; maxillary teeth smaller. From _Cratogeomys castanops subsimus_, found to the southwest, _ustulatus_ differs in: Tail shorter; hind foot smaller; upper parts darker, more rufous and less pinkish-buff; skull shorter; zygomata less widely flaring; palate shorter; rostrum averaging slightly narrower; nasals shorter; incisors narrower; maxillary teeth slightly smaller. For comparison of _ustulatus_ with the subspecies of _C. castanops_ to the southwest, see account of that subspecies to follow. _Remarks._--_Cratogeomys castanops ustulatus_ is a large-sized pocket gopher with a relatively larger, skull. In size o£ skull, _ustulatus_ is exceeded only by _C. c. subsimus_ found beyond the mountains in the southern part of Coahuila. In size, _ustulatus_ differs so markedly from _bullatus_ that the two can be distinguished easily by this feature alone. The skull of _C. c. convexus_ approaches that of _ustulatus_ in size, but is smaller in all respects, save breadth of rostrum. This pocket gopher is found commonly along the Río Salado and its watershed. Fallow cotton fields in the vicinity of Anahuac [= Rodríques], Nuevo León, are preferred living places. This subspecies was found at elevations as high as 1000 feet and as low as 600 feet.