The acknowledgment of gratitude always forms a pleasant paragraph. To the American Museum of Natural History, to Dr. Roy Chapman Andrews, and to the generous sponsors of the Central Asiatic Expeditions, I am indebted for the opportunity to explore the field in Central Asia. To Professor Charles P. Berkey thanks enough are due to fill this entire paper; and the pronoun “we”, which irked one of the censors in the first draft, was used because I feel that every chapter on the geology of Central Asia is in some part Professor Berkey’s work. Almost as inseparable from co-authorship in any paper on the stratigraphy of eastern Asia is Professor A. W. Grabau, whose masterly studies form the basis of comparison for all recent investigations. Special gratitude is due my good friend, Dr. Walter Granger, for helpful and constructive criticism; to the late Dr. Henry Fairfield Osborn and Dr. William . . .