Paleogene strata crop out along the western boundary of the San Joaquin Basin, in the Santa Barbara Embayment, and in the San Diego Basin, California. Eocene strata are represented by the Ulatisian and Narizian benthic foraminiferal stages (middle and late Eocene, respectively) of Mallory (1959). These provincial stages are used currently for both age assignment and interbasin correlation. Planktonic foraminifers in the Rose Canyon Shale, Poway Conglomerate, and the Matilija, Cozy Dell, Lodo, and Sacate Formations suggest that these formations, as a whole, range in age from late early Eocene to late middle Eocene. Previous authors assigned various elements of the aforementioned formations either to the Ulatisian or Narizian stages. Planktonic foraminiferid species suggest that the Ulatisian stage ranges in age from late early Eocene to early middle Eocene, and the Narizian stage ranges in age from early middle Eocene to late middle Eocene. The time-transgressive nature of ecologically controlled benthic foraminifers is apparent. Furthermore, stages based on benthic foraminifers are not valid means of correlation between tectonically discrete basins of deposition. The occurrence of Subbotina patagonica (Todd) in both the Rose Canyon Shale and Cozy Dell Formation suggests time-equivalence of the two units (early middle Eocene in age).