Bivalvia

Bivalvia also bivalves (noun, plural; Latin bis, two; valvae, a folding door): A class of marine, estuarine or freshwater bivalve mollusks, in which the body is enclosed within two calcareous valves, or shells; other names for this class are Acephala, Conchifera, Pelecypoda, Conchophora, Dithra, Lamellibranchia, Lamellibranchiata, Elatobranchiata, Cormopoda, Tropipoda, Aglossa, Elatocephala, Anodontoda and Lipocephala.