Practice question

Bivalvia were historically called Lamellibranchiata due to distinctive plate-like lamellar gills adapted for respiration and filter feeding. They display two lateral calcareous valves hinged dorsally, laterally compressed body, loss of distinct head and radula, expansive mantle forming large branchial chamber. Ctenidia enlarge into W-shaped demibranchs with ciliary tracts enabling high water pumping. Synonym Pelecypoda reflects hatchet-like foot for burrowing. Thus lamellibranch directly corresponds to class Bivalvia within Conchifera among molluscs historically defined by characteristic gill structure and shell form together.