On the eastern island in T.41.7 occurs rhyolite flow trending N.5°W, and the same flow occurs on the point on the south side of the Lake here trending N.5°E. This flow dips under porphyritic gray rhyolite tuff which occurs on the west side of the point in central T.41.7. Next east follow the trap intrusion forming Richardson Mountain, and then comes the fossiliferous sediment. About 10 feet of these are exposed striking N.55°E. and dipping 30°, S.E. Then after covered interval about 75 feet broad crop out three feet more of fossiliferous sediments and these dip under a mass of fragmental tuffs.