t, _jucundus_ differs in: Body larger; hind foot
averaging larger; upper parts darker, more ochraceous, and less buffy;
underparts darker, more buffy and less whitish; skull slightly
smaller; zygomata less widely flaring, especially in females; palate
shorter; nasals shorter; squamosal breadth less; mastoid bullae more
inflated; incisors narrower. From _Cratogeomys castanops subsimus_,
found to the south, _jucundus_ differs in: Body larger; tail shorter;
hind foot shorter; upper parts paler, more ochraceous and less
yellowish; skull smaller; zygomata less widely expanded laterally;
palate and nasals shorter; rostrum narrower; squamosal breadth less;
maxillary tooth-row shorter. From _Cratogeomys castanops bullatus_,
found to the north, _jucundus_ differs in: Body larger; tail averaging
longer; hind foot larger; color of upper parts more ochraceous and
less rufous; underparts darker, more buffy and less whitish; skull
larger, especially in length, in width across zygomata, in lengths of
palate, rostrum and nasals; mastoid and tympanic bullae less inflated;
squamosal breadth greater.

_Remarks._--_Cratogeomys castanops jucundus_ is large, exceeding
subsimus in dimensions of the body, but differing from _subsimus_ in
relatively smaller skull. Passage to the north and northeast by
_jucundus_ is at least partly blocked by inhospitable mountainous
country; the resulting semi-isolation may be one reason for the
distinctive characteristics of _jucundus_ compared with those of
_bullatus_ and _ustulatus_. Two specimens from Monclova, assigned to
_tamaulipensis_ by Nelson and Goldman (op. cit.:142), are here
referred to _jucundus_ on the basis of cranial characters and size.

Specimens were trapped in fallow irrigated fields in the vicinity
of Monclova. Others were taken in deep soils in desert flats.

_Specimens examined._--Total, 19, from: Hermanas, 1205 ft., 9; _1 mi.
S Hermanas_, 2; 1 mi. N and 13 mi. E Cuatro Cienegas, 2; 5 mi. N and
2 mi. W Monclova, 1; _2 mi. N and 1 mi. E Monclova_, 1; Monclova, 2
(BSC); Hisachalo [= Huisachalo], 2.

+Cratogeomys castanops sordidulus+ new subspecies

_Type._--Female, adult, skin and skull; No. 56614, Univ. Kansas Mus.
Nat. Hist.; 1.5 mi. NW Ocampo, 3300 ft., Coahuila; 16 December 1953;
obtained by Robert W. Dickerman, original number 2164.

_Distribution._--Desert plains of north-central Coahuila, surrounded
for the most part by higher mountainous country (see fig. 1).

_Diag