Population Studies
In the period of my study the populations of brush mice became smaller, perhaps owing to the severe winter of 1959-1960. In Cowley County, P. leucopus is now abundant and P. boylii rare where in December of 1959, the opposite was true. It is also possible, of course, that trapping has depleted the populations.
Conclusions
1. A new subspecies of brush mouse is named and described from southern Kansas.
2. The new subspecies has smaller eyes and a shorter tail and may be more primitive than P. b. attwateri.
3. No significant sexual dimorphism was noted in P. boylii.
4. In Kansas, P. b. attwateri is known only from a single locality; P. b. cansensis is known from only two localities, both in Kansas.
5. The cliff-dwelling habit of P. boylii probably isolates populations from one another.
6. The grasslands constitute a barrier for the brush mouse.
7. In Kansas, P. b. cansensis probably is an older population than P. b. attwateri.