A siliqua is digging the sand to bury. The siliqua is a species of bivalve molluscs of the Pharidae family found on the east coast of the United States. Like the other shells of its species, the Siliquar Catula uses his foot to dig and bury himself in the sand. His siphon is used to spit out the sand. Bivalve molluscs burrow to protect themselves from predators, waves, and high temperatures. The Siliqua is edible.