s 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.

_Diagnosis._--Size small (see measurements); tail long; hind
foot small; color dark, upper parts glossy Blackish Brown,
bases of hairs Plumbeous, sides Chestnut Brown, underparts
Pale Ochraceous-Buff or Warm Buff mixed with Plumbeous of
the hair bases; skull small, lightly constructed, relatively
deep; zygomata relatively weak; zygomatic breadth wider
posteriorly than anteriorly; rostrum relatively wide,
especially in males; nasals relatively long, truncate
posteriorly; interorbital constriction narrow; braincase
inflated; mastoid processes of squamosal only slightly wider
than zygomatic breadth; auditory bullae relatively large;
paroccipital processes weakly constructed, but extend
laterally over half the width of mastoid bullae; upper
incisors projecting anteriorly, rather than being strongly
recurved; maxillary teeth small.

_Comparisons._--From topotypes of _C. g. gymnurus_ from
Zapotlan, Jalisco, _C. g. atratus_ differs in: Body smaller
(total length averaging 300 in females compared with 341, a
male measured 315 compared with an average of 363); tail
shorter, hind foot smaller; color of upper parts darker,
glossy Blackish-Brown rather than reddish brown, underparts
paler; skull smaller (basilar length averaging 48.6 compared
with 57.5, a male measured 50.0 compared