Habitat. Attached by a byssus, mostly in sand and rubble mixtures but also in crevices and holes. Forms rafts on sand-covered rocks on the exposed north and east coasts. Frequently heavily encrusted by macroalgae.
Distribution. Throughout the lagoon from low in the intertidal to a few metres around the reef edge. Large densities occur along the more exposed eastern areas, notably at Pointe Coton.