Bottom samples from shallow to deep water were collected in Santa Monica Bay, California. The distributions of both living and dead foraminifera were determined. The majority of species living in the bay were found to have sharply restricted geographic and bathymetric ranges. Environmental factors such as current, nutrients, salinity, bottom sediments, and especially temperature are believed to control the distribution patterns of the benthonic species in the bay. The paleontological and oceano graphic applications of this work are discussed, and four new forms are described.