Semicassis pyrum, common name the "pear bonnet" or "common helmet", is a species of large sea snail, a marine gastropod mollusc in the family Cassidae, the helmet shells, bonnet shells and their allies.
Description
The shell has a light colour with a biconic shape, a notable large aperture, and ridges along the spire.
References
Powell A. W. B., William Collins Publishers Ltd, Auckland 1979