Douvilleiceras sp., an ammonite of Early Cretaceous age, was found in graywacke-type sandstone that is part of a narrow band of exposures in cliffs along the southern shore of the inlet to San Francisco Bay--an area regarded as in the type locality for the Franciscan group. Although the section is faulted and deformed, the sandstone of the fossil locality apparently is stratigraphically in the midst of part of a bedded sequence containing sedimentary rock types characteristic of the Franciscan group, such as graywacke-type sandstone, gray shale, radiolarian chert and shale, and greenstone. Thus the age of part of the Franciscan group as determined from the presence of Douvilleiceras sp. is Early Cretaceous, Albian. Because Franciscan rocks in other localities are overlain by beds containing Upper Jurassic fossils, it is proposed that the Franciscan group be assigned to both the Cretaceous and Jurassic(?) periods pending subdivision and more precise age designations within the group.