Hooper, 1938 Isabel Cr., 2200 ft., Santa Clara County, Calif. and vicinity. Jan. 6, Left Lockwood's place at 12:30, rolled in Burligame, then drove to San Jose, whence took road to east to Mt. Hamilton. Followed road by observatory on down northeast side of Mt. Hamilton to Isabel Cr. (c. to the U.S.G.S. sheet, 1906, where the road crosses the creek at about 2200 ft.) We camped and trapped on the floor of the flood plain near this point. The next day, after picking up the traps, we followed the road on down Arroyo Bayo (poor road, along creek bed) into San Antonio Creek drainage and San Antonio Valley thence north along Arroyo Mucho to Livermore. Trip from Isabel Cr. camp to Livermore took about 3 hrs. The country about Mt. Hamilton is typically Upper Sonoran. I saw no organisms which could be considered Transition indicators. The slopes of Mt. Hamilton and, as well of other "hills," are much as those seen on Mt. Diablo. Exposed faces, tops of ridges, and south facing slopes are grass covered with occasional oaks and digger pine. Shaded canyons have a growth