An analysis of the archaeology of two coastal areas of Central California gives strong support to the sequence of three culture periods proposed in 1939 for the prehistoric archaeology of the lower and middle Sacramento River Valley. For one area, the ocean coast of Marin County just north of San Francisco Bay, the first intensive excavations were made by archaeological field parties from the University of California during the summers of 1940 and 1941 ;.the data and conclusions have not been published previously. For the second area, around the shores of San Francisco Bay, few additions have been made to the artifact collections and field data since the latest full site report was made in 1926.3 However, the interpretation presented here comes from reappraisal of the original artifacts and notes from the limited number of published sites, and from study of museum collections from a greater number of smaller sites which have not yet been described in print.