Nummulites: Are they Stone Lentils, Frumentaries Stone or Devil’s Coins? No, are Giant Foraminifers

Abstract

The nummulites, which derive their name from the flattened discoidal shape of their shell, similar to that of a stone coin, were and are unicellular marine macroforaminifera, whose size varies from a few millimeters to about 12 cm in maximum diameter for some fossil species. Their abundance in certain rocks, now called nummulitic limestones, had already been noticed even by the ancient Egyptians and later Greeks and Romans. They were believed to be petrified grains, and under this appellation are described in the earliest printed books beginning with Agricola and Gessner. Their true origin remained disputed throughout the eighteenth century. The real nummulites or similar blackish discs of marcassite, according to popular tradition, were traces of the passage or work of the devil, who had lost them or had thus petrified the coins paid to commit a crime or a spell, making it in the end fruitless for the perpetrator.