ossil
vertebrates formerly belonging to the California Institute of
Technology, but now the property of the Los Angeles County Museum.
The specimens had been lent by the late Professor Chester Stock to
Professor Hall and Dr. Wilson for study and report. All
measurements herein are in millimeters.

#Thomomys umbrinus# (Richardson)

Material referable to _Thomomys_ consists of a nearly complete cranium,
L.A.C.M. (C.I.T.) No. 3952, with nasals, maxillary teeth, and lower
parts of braincase missing and zygomata broken; four rami (unnumbered),
one of which is badly broken; and two isolated molariform teeth. The
skull has a sphenoidal fissure, a feature typical of the _umbrinus_
group of _Thomomys_. The fossil specimens closely approximate in size
the living subspecies _Thomomys umbrinus analogus_ Goldman. _Thomomys_
is not known from the vicinity of the cave at the present time and has
not been reported from southwestern Nuevo Leon, even though there has
been extensive collecting for pocket gophers there in recent years. To
my knowledge the nearest record of occurrence of modern _Thomomys_ is a
series of _Thomomys umbrinus analogus_ from 12 miles east of San Antonio
de las Alazanas at an elevation of 9000 feet in the state of Coahuila
(Baker, 1953:511), approximately 85 miles to the northwest. The fossil
gophers are not from the talus of the cave floor, which is evidently of
subrecent origin, but from the Pleistocene deposits below. Close
resemblance to the living subspecies _T. u. analogus_, however,
indicates that these remains are not so old as some of the other geomyid
fossils from the cave.

#Cratogeomys castanops# (Baird)

Seven rami pertain to the genus _Cratogeomys_. All except three,
L.A.C.M. (C.I.T.) Nos. 2974, 2978, and 3954, lack cheek teeth and the
posterior processes are missing on most of the mandibles. No. 2974 is
smaller than the other specimens, and probably is from a young
individual. No. 3954 may have been fossilized at an earlier date than
the other six jaws; however, it is comparable to them in size and
morphology. Also present in the deposits are three limb bones of
_Cratogeomys castanops_. One, a right humerus bearing L.A.C.M. (C.I.T.)
No. 2982, is slightly larger than that of the pocket gophers living in
the area now. Two tibias, L.A.C.M. (C.I.T.) Nos. 2983 and 2984, complete
the material referable to this species.

_Cratogeomys castanops planifrons_ (see Russell and Baker, 1