PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES FOURTH SERIES Vol. XXXVI, No. 17, pp. 511-530; 5 figs.; 4 tables. April 18, 1969 PLEISTOCENE INVERTEBRATES FROM NORTHWESTERN BAJA CALIFORNIA DEL NORTE, MEXICO By James W. Valentine and Robert R. Rowland Department of Geology, University of California, Davis 95616 Abstract: Six fossil localities on marine terraces between the Tijuana Playas and Rosarito Beach have yielded 83 identified species of mollusks together with a few other invertebrate forms. The assemblages are small (43 moUuscan species at the most diverse locality) but represent several distinctive environments: an exposed sandy shore or nearshore association ; gravel shore or nearshore associations ; and quiet-water lagoon or marine pond associations. Assemblages from elevations below about 100 feet include southern species and probably represent the Late Pleistocene Verdean Province. Assemblages from higher elevations, between 120 and 130 feet, do not include species that are sensitive biostratigraphic indicators within the Pleis-tocene. INTRODUCTION Road cuts and quarries associated with the construction of new roads be-tween the International Boundary and Rosarito Beach, northwestern Baja Cali-fornia, contain exposures of fossiliferous marine Pleistocene strata (fig. 1). The fossils are largely mollusks and represent chiefly sandy-bottom associations not previously reported from this region. In this paper these invertebrate fossil as-sociations are described, evidence is presented to support an interpretation of their environmental backgrounds, and their place in the Pleistocene of southern California and Pacific Baja California is discussed. Previous Work Pleistocene marine fossil assemblages from the coastal region of Baja Cali-fornia at Rosarito Beach and northward have been reported previously (Valen-[511] Marine Blofog'cal Laboratorv / LIBRARY APR 2 9 1969
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