Scale-sided Piddock

Found over mud, shale, and hard substrate, of the ocean floor, where these clams bore holes, and construct chimneys, using tiny bits of rock, cemented with calcium carbonate, which become their burrows. Around exposed bays, and outer coasts, in the lower, intertidal areas.
Eastern Pacific - USA to Mexico

Most Bivalves are permanently anchored in fissures or depressions in the rock surface of the reef, some may become covered in algae and other marine life.
Other Bivalves swim free, either by a well developed foot or propelled along by a jet of water from their mantle cavity.