Cooper, 1936 1 mi. W Summit Mt. Diablo, 3000 ft., Contra Costa Co., Calif. Feb. 16, Members of "overnight" party to Mt. Diablo = D. H. Johnson, F. G. Palmer + E. T. Cooper. Time of departure = 4 P.M. Time of return with traps 10 A.M. Weather: Rain at Berkeley; cloudy at Lafayette + Walnut Cr.; cold heavy fog (or within clouds) from approximately 2000 ft. on mountain on up, ± 30 mile wind. At Walnut Cr. we followed the highway leading northwestward toward Pittsburg then turned north eastward through the west gate of the Mt. Diablo State Park. Following this "west" road on up toward the summit of the mountain to " Laurel Dell" and "Juniper Flat (or Mook)"; the names applied to two camp grounds near the main road and approximately 1½ mi. (by road) from the crest of the mountain. Here we turned left (north) through the camp ground to the "Deer Flat" trail (1¼ miles from the Park boundary). We followed this trail for several hundred feet until we passed through the gate marking the Park limits. Just outside the Park boundary we set out our traps - 150 for the 3 people. The superficial layers of the substrate