Arcoida

The Arcoida is an order of marine bivalve mollusks belonging to the subclass Pteriomorphia. These bivalves are characterized by their solid shells, which can be elongated or circular-oval and are often heavily ribbed. They possess a fibrous periostracum and a hinge with vertical denticulations.1

Many species in the Arcoida, such as those in the genera Arca and Barbatia, attach themselves to surfaces using byssal threads. Other species, like those in the genus Anadara, burrow shallowly into sand and silt. Some ark shells, such as Anadara senilis and Anadara granosa, have been a food source for humans for a long time. There are approximately 150 known species within this order.21