He'eia, Oahu, 2 feet, 40 mm

Locally common in groups on branching and Montipora coral at any depth.  The aperture is white and it tends to be heavily encrusted by coralline algae.  They consume coral tissue, leaving scars for algae and disease to proliferate.  Attains 1.7 inches, 40 mm.  Red Sea to Hawaii and French Polynesia.  Formerly known as Drupella elata.