Close comparison with _C. g. imparilis_ from Patzcuaro, Michoacan, is not needed, _but C. g. tellus_ differs especially in: Color of underparts and hairs of feet whitish rather than brownish; skull smaller; zygomatic breadth greater; interorbital constriction broader; nasals longer; maxillary tooth-row longer. _Measurements._--Averages of three adult females, including type, and the measurements of an adult male (in parentheses) from the type locality are: Total length, 338 (356); length of tail, 92 (87); length of hind foot, 45 (47); occipitonasal length of skull, 64.1 (68.7); basilar length, 55.3 (61.4); zygomatic breadth, 42.7 (48.0); interorbital breadth, 9.6 (11.4); greatest height of cranium, taken from palate perpendicular to line touching two highest points on top of skull, 23.9 (25.3); least depth of rostrum, 10.6 (11.7); breadth of rostrum, 14.7 (16.5); length of nasals, 23.6 (25.2); width across mastoid processes of squamosal, 43.8 (49.7); height of occiput, 18.1 (19.9); length of maxillary tooth-row, 14.6 (15.2). _Remarks._--The distribution of _C. gymnurus_ is spotty; its occurrence seemingly depends on edaphic conditions. The isolation of soils with textures suitable to this animal has resulted in the isolation of gopher populations. The distribution is similar to that of species occurring on islands. In this instance, however, the populations of gophers are separated by soils of heavy texture which render burrowing difficult or impossible for gophers. Such conditions have led to a high degree of subspeciation in a relatively short distance. For example, four subspecies of _C. gymnurus_ occur in Jalisco, and, all are within an area scarcely fifty miles in diameter. _Cratogeomys gymnurus tellus_ is the northernmost subspecies of _C. gymnurus_. It is known from only the vicinity of Tala, west of Guadalajara, and its range probably is not much more extensive than this because of the localized distribution of suitable soils. _Specimens examined._--Total number ten, as follows: 3 mi. W Tala, type locality, 5; 1 mi. NE Tala, 3; 1 mi. S El Refugio, 2. =Cratogeomys gymnurus atratus= new subspecies _Type._--Female, adult, skull and skin, No. 31880 Mus. Nat. Hist., Univ. Kansas; from Top of Cerro Viejo de Cuyutlan, 9700 ft., 19 mi. S and 9 mi. W Guadalajara, Jalisco, Mexico; obtained on February 17, 1949, by J. R. Alcorn, original No. 7902. _Range._--Known only from the type locality on the Cerro Viejo.