ETYM Pref. bi- + valve.
(Zoology) Used of mollusks having two shells (as clams etc.); SYN. bivalved.

ETYM French bivalve; bi- (Latin bis) + valve valve.
Marine or freshwater mollusks having a soft body with platelike gills enclosed within two shells hinged together; SYN. pelecypod, lamellibranch.
Marine or freshwater mollusk whose body is enclosed between two shells hinged together by a ligament on the dorsal side of the body.
The shell is closed by strong “adductor” muscles. Ventrally, a retractile “foot” can be put out to assist movement in mud or sand. Two large platelike gills are used for breathing and also, with the cilia present on them, make a mechanism for collecting the small particles of food on which bivalves depend. The bivalves form one of the five classes of mollusks, the Lamellibranchiata, otherwise known as Bivalvia or Pelycypoda, containing about 8,000 species.