Distributions of living Foraminifera were analyzed from 76 stations in the Gulf of California. Approximately 220 living species were identified.

Standing crops of living Foraminifera at depths greater than 1,000 fm average 26.5 specimens/10 ml of wet surface sediment. Standing crops are larger in shallow water. Areas of unusually large living populations at the head of the Gulf may be due to river influence, hypersalinity, or the effect of the silty substrate. Large living populations at three locations on the border of the Gulf may be due to high organic production caused by upwelling.

The following boundaries between depth biofacies are indicated by ranges of 66 common species--15-20 fm, 30-35 fm, 40-50 fm, 70 fm, 90 fm, 200 fm, 400-500 fm, 600-800 fm, 1,000 fm, 1,300 fm, and 1,500 fm. Ecological explanations for these 12 depth assemblages must await further understanding of the physical and chemical environments of the area.

Relative rates of deposition based on living-total ratios of Foraminifera suggest a very slow overall present rate of deposition in the Gulf, with small areas of faster deposition around the borders. The deposition rates south of the entrance to the Gulf, in depths greater than 1,000 fm, appear to be much faster than those within the Gulf.