Trap-lines totaling one hundred mouse traps, set on August 6 and August 18, took on the first nights two prairie white-footed mice, one house mouse, and one young thirteen-striped ground squirrel. More white-footed mice were taken on later nights. Many ground squirrels were taken in larger traps at the mouths of their burrows; most of these were young of the year, and all of them were very fat in preparation for their approaching hibernation. _Cultivated field habitat_: _Scalopus aquaticus machrinus._ Prairie mole. 1. _Peromyscus maniculatus bairdii._ Prairie white-footed mouse. 23. _Microtus ochrogaster._ Prairie vole. 1. _Mus musculus musculus._ House mouse. 2. _Sylvilagus floridanus mearnsii._ Mearns cottontail. 2. Cultivated fields occur throughout the region about the woods, but the only ones in which trapping was done were wheat stubble-fields. After the wheat was cut off these stubble-fields grew up rather thickly to weeds. On the ground there were a number of fallen heads of wheat and some shelled-out grain, furnishing abundant food for mice. Seventy mouse traps set in a wheat stubble-field just north of Warren Woods, caught on the first nights, August 13 and August 29, sixteen prairie white-footed mice. Other white-footed mice and two house mice were taken on later nights. Several cottontails were seen in this field, and a few mole ridges were noted. A prairie mole was taken by Clifford Reid in a grassy patch at the edge of a garden. In another wheat field the Helming boys picked up a prairie vole. _Orchard habitat_: _Peromyscus leucopus noveboracensis._ Northern white-footed mouse. 1. _Microtus pennsylvanicus pennsylvanicus._ Pennsylvania vole. 2. No especial study of the mammal life of the orchard was made, and no intensive trapping was done in the habitat. However, the orchard cannot be included in any of the other habitats recognized in the region. A northern white-footed mouse was caught alive by the Helming boys in an orchard on July 16. A vole was seen to cross a road in a small orchard on July 15; a trap was set and two Pennsylvania voles secured, one a young of the year. _Edificarian habitat_:[1] _Blarina brevicauda talpoides._ Short-tailed shrew. 1. _Peromyscus leucopus noveboracensis._ Northern white-footed mouse. 2. _Rattus norvegicus._ Norway rat. 4. _Mus musculus musculus._ House mouse. 22. _Sylvilagus floridanus mearnsii._ Mearns cottontail. 2. From time to time a few traps were set in the old farmhouse and in the barn and other outbuildings of our camp. In these buildings northern white-footed mice, Norway rats, and house mice were taken. Several cottontails were seen in and under the old barn. The Helming boys trapped a short-tailed shrew and also house mice and a white-footed mouse in the basement of their house. RECORDS OF THE NUMBER OF EMBRYOS