Shell completly white, both exterior and interior, and very thick. Aperature
nearly circular, apex very tall and centered. Exterior often completely
encrusted with pink coralline algae.
Alaska (Aleutian Islands) to Baja California. Common on British Columbia coast.
On rocks in protected sites near areas of heavy surf. Usually subtidal
to 200ft, but also in low intertidal. Associated with encrusting pink coralline
algae, which is it's main food. Usually it is found completely covered
in this favorite food, giving it great camouflage. Empty shells often found
on coastal beaches.