The Areas and Problems investigated.—In northwestern California and southwestern Oregon, where the Sierra Nevada, Cascade and Coast ranges meet, there is a plexus of mountains which may for convenience be called the Klamath mountain group. The Klamath mountains extend from the fortieth to near the forty-fourth parallel, and include the Yallo Bally, Bully Choop, South Fork, Trinity, McCloud, Scott and Salmon mountains of California, and the Siskiyou, Rogue river, and perhaps others in Oregon. The outline of the Klamath mountain group is indicated on the accompanying map by a heavy broken line. The map (plate 4) contains nearly all the localities mentioned in this paper.
In his excellent correlation paper on the Cretaceous,* Dr C. A. White has given a bibliography and concise review of the work already done on the rocks of that system in the Pacific border region from California to Alaska. The present state . . .