In any one of the lists of "Specimens examined" beyond, the order of arrangement of the localities is from north to south. Those localities listed in Roman type are represented on the distribution map (Figure 1) by blacked-in circles. Each of several circles covers two or more localities because the localities are close together. In any such instance the northernmost place is listed in Roman type and the names of the other places follow in Italic type. Measurements in millimeters are given in table 1 for females and in table 2 for males.
+Cratogeomys castanops convexus+ Nelson and Goldman
1934. _Cratogeomys castanops convexus_ Nelson and Goldman, Proc. Biol. Soc. Washington, 47:142, June 13, type from 7 mi. E Las Vacas [= Villa Acuña], Río Grande Valley, Coahuila (opposite Del Río, Texas).
_Distribution._--Extreme northern Coahuila, east and north of the Serranías del Burro (see fig. 1).
_Diagnosis._--Previously known from only one specimen, a subadult female, this subspecies has not been well diagnosed. At hand we have five near topotypes of _convexus_ (including two adult females and one adult male) and specimens assignable to this subspecies from several other localities. This subspecies may be characterized as follows: Size medium (see tables 1 and 2); dorsal profile of skull convex in females and flat, especially posteriorly, in males; zygomata weakly constructed and not widely flaring; mastoid and tympanic bullae inflated; nasals short; rostrum broad and short; maxillary teeth large.
[Illustration: ~Fig. 1.~ Geographic ranges of the subspecies of _Cratogeomys castanops_ found in Coahuila, México.
Guide to subspecies 4. _C. c. bullatus_ 8. _C. c. subsimus_ 1. _C. c. convexus_ 5. _C. c. ustulatus_ 9. _C. c. goldmani_ 2. _C. c. consitus_ 6. _C. c. jucundus_ 10. _C. c. subnubilus_ 3. _C. c. sordidulus_ 7. _C. c. excelsus_ 11. _C. c. planifrons_]
_Comparisons._--From topotypes of _Cratogeomys castanops angusticeps_ Nelson and Goldman, found to the north and east across the Río Grande in Texas, _convexus_ differs in: Body larger; upper parts more reddish, especially on sides; skull with zygomata less heavy, nasals broader, pterygoids smaller, maxillary teeth larger. For comparisons of _convexus_ with the subspecies of _C. castanops_ found to the west, south and southeast, see accounts of the subspecies to follow.
