We often come across these empty shells of  Tresus capax the Fat Gaper on the shores of Taylor Beach. They live buried in the sand in the shallow water offshore. Around the opening of the siphon, Tresus capax  has small palps around each opening which distinguishes it from other bivalves.

Fat Gaper : ( Tresus capax)

Classification::
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Veneroida
Family: Mactridae
Genus: Tresus
Species: Tresus capax (Gould, 1850)

The Fat Gaper, Tresus capax . Note the size in comparison to a glove.

Useful References: E-fauna BC page on bivalve Molluscs: