Comparisons.--From Cratogeomys castanops convexus, found to the north, bullatus differs in: Hind foot shorter; skull much broader in relation to length; rostrum narrower but, relative to length of skull, wider; tympanic bullae slightly more inflated; incisors and maxillary teeth smaller. From topotypes of Cratogeomys castanops angusticeps, found across the Río Grande and upstream from localities where bullatus is known to occur, bullatus differs in: Body slightly smaller; color paler, especially on sides; skull shorter and broader; rostrum shorter and broader; nasals shorter; mastoid and tympanic bullae more inflated; maxillary teeth smaller. For comparisons of bullatus with the subspecies of C. castanops found to the west and south, see accounts of the subspecies to follow.
Remarks.--Cratogeomys castanops bullatus in small size resembles C. c. tamaulipensis Nelson and Goldman of the lower Río Grande Valley in Tamaulipas, but the two differ markedly in cranial features. Cratogeomys c. bullatus is smaller than convexus but these two subspecies resemble each other in color and cranial characters. Both have an arched skull, inflated mastoid and tympanic bullae, short nasals, and a short rostrum. Comparison of bullatus with angusticeps, which occurs across the Río Grande but not directly opposite the range of bullatus, indicates that these two subspecies are less closely related than bullatus is to tamaulipensis and convexus.
Cratogeomys castanops bullatus is especially common in sandy soils in the vicinity of Nava where the mounds were in fallow irrigated fields and other open places between extensive live oak thickets. South and west of the Río Grande the animals were less abundant and lived in heavier soils usually as individuals or in small groups. Specimens were taken at elevations from as low as 800 feet to as high as 2,000 feet.
Specimens examined.--Total, 24, from: 2 mi. S and 6-1/2 mi. E Nava, 810 ft., 2; 2 mi. S and 12 mi. E Nava, 800 ft., 1; 3 mi. S and 12 mi. E Nava, 800 ft., 4; 29 mi. N and 6 mi. E Sabinas, 5; 10 mi. E Hacienda La Mariposa, 2000 ft., 1; La Gacha [= La Concha], 1600 ft., 8; 8 mi. S and 8 mi. E Hacienda La Mariposa, 1900 ft., 1; 9 mi. S and 11 mi. E Sabinas, 1050 ft., 2.
Cratogeomys castanops ustulatus new subspecies
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 of 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.