any of an order (Foraminifera) of large, chiefly marine, organisms usually having calcareous shells. These form the bulk of chalk and some limestones.

marine microorganism having a calcareous shell with openings where pseudopods protrude

Large, chiefly marine rhizopod protozoans usually having calcareous shells often perforated with minute holes for protrusion of slender pseudopodia; of the Order Foraminifera

Protozoans that belong to the subclass Sarcodina, order Foraminifera, that have a test of one to many chambers composed of secreted calcite or agglutinated particles.

Foraminifer - Any protozoan belonging to the subclass Sarcodina, order Foraminifera, characterized by the presence of an external shell or one or many chambers composed of secreted calcite or of composite particles. Most foraminifers are marine but freshwater forms exist. Range: Cambrian to the present.

a group of single-celled eukaryotes that secrete distinctive, chambered calcium carbonate shells or 'tests'.