Benthic foraminiferal species from a part of the central Oregon shelf are grouped into four distinct bathymetric faunas. Elphidiella hannai and Buccella spp. are indicative of Fauna A (17-50 m). Fauna B (50-100 m) is characterized by Buliminella elegantissima and Elphidium magellanicum. In the rocky area off Cape Arago Cassidulina californica, C. limbata, Cibicides fletcheri, and C. lobatulus become dominant. Spiroplectammina biformis, Textularia earlandi, and Trifarina angulosa are important species of Fauna C (100-175 m). Abundant species of Fauna D (175-339 m) include Eggerella advena, Epistominella exigua, and Uvigerina juncea.

Species diversity increases offshore to a maximum of about 35 benthic species near 100 m and then decreases slightly with depth. The standing crop is small nearshore, increases to a maximum of approximately 300 specimens per 20 cm³ between 125 and 150 m, and then declines. The total benthic population reaches a maximum of approximately 6,000 specimens per sample between depths of 150 and 175 m. Values then decrease to about 2,000 specimens at 339 m. A maximum of 15-20 percent live benthic specimens occurs near 50 m. Planktonic Foraminifera normally constitute less than 10 percent of the total population. Maximum percentages generally are in water shallower than 100 m, whereas maximum specimens per sample are at the deepest stations. Porcelaneous specimens do not exceed 6 pe cent of the benthic population. Agglutinated Foraminifera are more abundant than calcareous specimens at depths greater than 100 m.

Miscellaneous biofacies trends indicate that: thecameobians are most abundant between 50 and 125 m; statoliths and otoliths are most abundant between 75 and 200 m; the largest number of ostracods are between 25 and 150 m; and radiolarians generally predominate over Foraminifera below 250 m.

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