Since 1925, much detailed work has been done on the stratigraphy and faunas of the marine Eocene of the west coast of North America. This work is still in progress, and, undoubtedly, the conclusions presented in this paper will be modified. However, it would seem worth while to give a summary of present knowledge of the sequence of the West Coast, in order to state the problems at hand and to give the stratigrapher a better basis for recognizing the important divisions.
The correlations here given are based principally upon the molluscan faunas. A considerable amount of work is now being done upon the foraminifera; undoubtedly, this will prove to be important and will serve as a check on the conclusions based upon the other fossil groups.
A large proportion of the molluscan species in the marine Eocene deposits of western North America are indigenous. Many of the same . . .