A small, hard, yellow-white shell with a humped back and margins thickened into a flared rim, rarely more than 4 cm (1.6 in) long. It lives on shallow reef flats, grazing algae at night and spending the day wedged under a stone, which is where anyone looking for it should look.
This is the shell that was money. For centuries it circulated as currency across West Africa, South Asia and parts of 🇨🇳 China, shipped in barrels from the 🌊 Indian Ocean and counted out by the thousand, and the trade in it was tied directly to the trade in people. Its scientific name records the fact: Monetaria, from the Latin for mint.
The living animal looks nothing like the polished object in a shop. Two flaps of mantle fold up over the shell from below and cover it completely, dark and papillate, laying down new shell material from the outside. Startle it with a torch and the mantle peels back in a second or two, which is the best thing to watch and the hardest to photograph.
- small yellow-white shell with a swollen back and thickened flared margins
- an irregular ring of darker color often visible on the back
- usually under a stone on a shallow reef flat
- shell to about 4.6 cm
