Foraminifera or forams, order of the subphylum Sarcodina, Phylum Sarcomastigophora, are unicellular marine organisms either on the bottom or floating in the water. They have either a usually multi- chambered shell, or reticulate pseudopodia or, usually both. Planktonic species have a vacuolated outer layer of protoplasm. The shells are calcareous, but are occasionally chitinous, siliceous, or gelatinous with embedded foreign bodies. The planktonic forams are so numerous that their empty shells form an ooze which covers enormous areas of the ocean floor. They have existed since the Cambrian andare widely used by geologists for biostratigraphical zonation.