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 this area and southeastern Kansas. Activities of other rodents may have confined the brush mouse ecologically to cliffs. Although the grasslands are a barrier to further intrusion by the brush mouse into Kansas, one cannot assume that they alone confined the brush mouse to cliffs. Such an assumption would not explain its absence on systems of cliffs similar to and near other systems of cliffs on which it is found in the non-grassy Ozarkian habitats of Arkansas, as was noticed by Black (1937). Such an assumption would not indicate why the size of the cliff-systems is correlated with the absence or presence of the brush mouse on the northeastern margin of its geographic range. Parasites found on _P. b. attwateri_ include three individuals of the laelapid mite, _Haemolaelaps glasgowi_. Two of these mites were removed from a live mouse. Two larval Ixodid ticks, _Ixodes_ possibly _cookei_, were removed from the pinnae of the ears of a specimen of _cansensis_ from the type locality, 4 mi. E Sedan, Chautauqua County. Four larval Ixodid ticks, _Dermacentor_ possibly _variabilis_, were removed from the pinnae of the ears of a live specimen of _cansensis_ from 3 mi. W Cedar Vale, in Cowley County. TABLE 2. STOMACH CONTENTS OF 38 BRUSH MICE FROM SOUTHEASTERN KANSAS IN WINTER AND SPRING.