the eyes are less protuberant and
the tail is shorter in _P. b. cansensis_ than in the latter. I suggest
that _P. b. cansensis_ occurred in what is now known as Kansas before
_P. b. attwateri_ entered this area by way of the Ozark Mountains. The
occurrence of a mouse of "the _truei_ or _boylei_ group" (Hibbard,
1955:213) in southwestern Kansas in the Jinglebob interglacial fauna of
the Pleistocene adds little to support the thesis outlined above, but is
not inconsistent with the thesis. Incidentally, the geographic
distribution of _P. boylii_ may differ somewhat from that shown by Blair
(1959:fig. 5); whereas he has mapped the distribution of _P. boylii_ to
show disjunctivity in _P. b. attwateri_ and homogeneity in the
distribution of other subspecies of the brush mouse to the westward and
southward, disjunctivity actually occurs frequently also in the western
and southern subspecies.

_Ecology_

In Kansas the brush mouse is confined to systems of cliffs, the faces of
which range in height to at least 40 feet. The highest cliffs--some
approximately 100 feet--on which brush mice are known to occur in Kansas
are along Shoal Creek, Cherokee County. The brush mouse is found on low
bluffs that are parts of higher systems, but in Cherokee County the
mouse was not obtained from low bluffs separated by even a few miles
from the cliff-system along Shoal Creek. As implied above the brush
mouse is adapted for a scansorial mode of life; but other mice and rats
inhabit the rocky crevices of low bluffs. Whereas the brush mouse is
well adapted for living on high cliffs it seems that the other rodents
are better adapted for life on low cliffs. _Sigmodon hispidus_ was
obtained from the low, limestone cliffs mentioned previously. From most
low bluffs in southeastern Kansas (and on some high bluffs outside the
geographic range of _cansensis_) _Peromyscus leucopus_ was obtained. In
Cowley County the brush mouse was abundant when _P. leucopus_ was not
and _vice versa_ during this study. _Sigmodon hispidus_ did not
associate with the brush mouse in any area, although _S. hispidus_ was
often trapped in grassy areas adjacent to cliffs and on the grassy
crests of the hills. Except at the locality in Cherokee County, the pack
rat, _Neotoma floridana_, was found in association with the brush mouse.
_Microtus ochrogaster_ was the must abundant rodent in adjacent
southwestern Missouri (Jackson, 1907) before _Sigmodon_ thoroughly
infiltrated thi