y have the same characteristic
shape as the holotype. Nevertheless, the two rami mentioned above are
significantly larger than in adult males of modern _Heterogeomys_ and
are especially larger than in females. Another jaw fragment, L.A.C.M.
(C.I.T.) No. 2385, is seemingly as large as, or perhaps larger than,
the holotype, although the posterior part of the ramus behind the
alveolus of m2 is missing. An additional unnumbered ramus is of somewhat
lighter construction than the holotype, but is important since it bears
not only the incisor and p4 but also the first two lower molars. The
only other material referable to _Heterogeomys onerosus_ is a
fragmentary and isolated lower molar tooth that has a single posterior
enamel blade, a feature characteristic of a number of Recent genera of
pocket gophers, and some limb bones which are slightly larger than
corresponding elements in Recent species of _Heterogeomys_.

_Remarks._--Pocket gophers do not inhabit caves; therefore gophers were
brought into the cavern probably by birds of prey, the remains of which
were common in the deposits (Miller, 1943:152-156), or conceivably by
carnivorous mammals. Since most of the raptorial predators that would
prey on pocket gophers do not have a wide hunting territory, it is
likely that the gophers were taken within a short distance of the cave.
The presence of the genus _Heterogeomys_ in the deposits strongly
suggests a tropical situation in the vicinity of the cave when these
gophers were taken, because the distribution of this genus today is
entirely within the Tropical Life-zone.

Since the presumably early time when tropical conditions, or more nearly
tropical conditions, prevailed at San Josecito Cave, climatic shifts
account for a humid boreal environment there and its associated fauna.
Findley (_lit. cit._:635-636) reports from San Josecito the remains of
the boreal shrew _Sorex cinereus_ that today occurs no nearer than 800
miles to the northward in the mountains of north-central New Mexico. As
he points out, that species requires hydric communities of cool
climates, and in the Wisconsin Glacial age such climates probably
prevailed in the high mountainous region where San Josecito is located.
Since the time when a more mesic boreal environment occurred at San
Josecito, climatic shifts have favored more xeric conditions as are
found in the vicinity of the cave today. The more arid environments
would support the occurrence of _Cratoge