Foraminiferan. Macro photograph of a foraminiferan. Foraminifera are single-celled marine protozoa that construct and inhabit a calcium carbonate shell (white) composed of several chambers. Most live on the sea bottom, feeding using amoeba-like pseudopodia that are extruded through pores in the shell (also called a test). This specimen is from Japan. Magnification: x34 when printed at 10 centimetres wide.