with an average of
59.0); zygomata more weakly constructed; zygomatic breadth
less, and wider posteriorly than anteriorly; braincase more
inflated; nasals shorter; rostrum relatively narrower and
shallower; width across mastoid processes of squamosals
less; paroccipital processes less strongly constructed,
extending farther laterally; upper incisors projecting
anteriorly rather than being strongly recurved; maxillary
teeth smaller (length of maxillary tooth-row averaging 11.2
compared with 14.9).

From _C. g. tellus_, that occurs to the northwest, _C. g.
atratus_ differs in: Body smaller; hind foot slightly
smaller; upper parts darker; underparts Pale Ochraceous-Buff
rather than creamy-white; skull smaller (see measurements);
zygomatic breadth less, and wider posteriorly than
anteriorly; nasals shorter, truncate posteriorly rather than
emarginate; rostrum narrower and shallower; maxillary teeth
smaller.

From near-topotypes of _C. g. inclarus_ from the Sierra
Nevada de Colima, _C. g. atratus_ differs in: Body slightly
smaller; hind foot smaller (averaging 42 compared with 49);
color of upper parts near the same, underparts paler; skull
smaller, narrower, weaker in construction; zygomatic breadth
less; nasals relatively longer, but actually shorter
(averaging 19.7 compared with 20.3); upper incisors
projecting anteriorly rather than being recurved; maxillary
teeth smaller.

_Measurements._--The type and an adult female (its
measurements in parentheses) yield measurements as follows:
Total length, 300 (299); length of tail, 78 (83); length of
hind foot, 43 (40); occipitonasal length of skull, 56.3
(55.5); basilar length, 49.3 (47.8); zygomatic breadth, 37.9
(36.5); interorbital breadth, 8.7 (8.1); greatest height of
cranium, as explained above, 21.6 (20.7); least depth of
rostrum, 9.2 (8.8); breadth of rostrum, 12.8 (12.7); length
of nasals, 19.4 (20.0); width across mastoid processes of
squamosal, 38.2 (37.1); height of occiput, 16.9 (17.3);
length of maxillary tooth-row, 11.9 (11.3).

_Remarks._--_Cratogeomys gymnurus atratus_ is the smallest
subspecies known for the species, and is so distinct from
other described subspecies, that it is difficult to select
one as the closest relative. In color, _C. g. atratus_