​NUMMULITE, NUMMULITES, A. d’Orbigny’s name for a genus of Perforate Foraminifera (q.v.), distinguished by the flattened, lenticular discoid shell of many turns, finely perforated; chambers subdivided by incomplete septa into squarish chamberlets. This genus is especially abundant in Eocene Limestones, which attain great thickness around the Mediterranean basin; the Pyramids of Egypt are built of it.