The climax forest of the region is dominated by the beech, _Fagus grandiflora_, and the sugar maple, _Acer saccharum_. The trees in this forest are very large, so that the forest crown is high and the shade dense. Only a few small trees occur and these are mostly young beeches and young sugar maples. The underbrush varies much in height and denseness; mostly it is quite open, so that one can easily walk through the forest, but in a few places the growth is more dense. Common members of the underbrush on the higher ground are the small beeches, sugar maples, and the spice-bush, _Benzoin aestivale_; while on the lower benches along the river seedlings of the paw-paw dominate the undergrowth. The ground is heavily covered by decaying leaves and a little dead brush and fallen branches, but nearly all the logs have been removed. Early in the spring a thick growth of herbs covers the ground, but by July the herbs are mostly gone, only a few remaining, and there are many small bare areas covered only by leaves. The soil under this forest seems to be mainly clay; in spring or after heavy rains pools of water are formed, and these remain for a long time. Between July 21 and August 27 a total of two hundred and eighty-five mouse traps set in the upland forest took on the first nights one short-tailed shrew and thirty northern white-footed mice. In addition to these species pine voles and a jumping mouse were trapped on days after the first. One shrew was caught alive August 30, as he was running about on the forest floor at 7:30 A.M. A few tracks of raccoon were seen from time to time on the road leading through the woods. A few fresh burrows of woodchucks were noted at the edges of benches and of ravines. A few red squirrels were seen at different times and two collected. Fox squirrels were rare, being noted only a few times; Mr. Norman A. Wood also saw these squirrels on two occasions in May. One cottontail was shot, in the climax forest. Mr. Wood collected a chipmunk in the climax forest on May 15, 1918, and saw another in the same habitat in May, 1919. _Aerial habitat_: Bats were seen on a few evenings, flying about over the climax forest, and over the adjacent region, but they were extremely rare, and efforts to shoot a specimen failed. MODIFIED AND ARTIFICIAL HABITATS _Second-growth forest and scrub habitat_: _Mustela noveboracensis noveboracensis._ New York weasel. 1. _Mephitis nigra._ Eastern skunk. 1. _Peromyscus leucopus noveboracensis._ Northern white-footed mouse. 5. _Microtus pennsylvanicus pennsylvanicus._ Pennsylvania vole. 4. _Mus musculus musculus._ House mouse. 1. _Marmota monax monax._ Southern woodchuck. 1. _Sciurus hudsonicus loquax._ Southern red squirrel. 1. _Sylvilagus floridanus mearnsii._ Mearns cottontail. 5.