Punalu'u, Oahu, 4 feet, 24 mm

Okoe Bay, Hawaii, 30 feet

Kewalo Pipe, Oahu, 50 feet

Puako, Hawaii, 40 feet

Common on Porites coral leaving a permanent home scar, where it grazes live tissue and weakens the host. The white shell is heavily encrusted by coralline algae and often eroded, and the aperture is violet.  Attains 1.9 inches, 47 mm.  Red Sea to Japan, Hawaii, Rapa Nui, and the Galapagos.  Formerly known as Coralliophila neritoidea.