Mollusca

A phylum of the subkingdom Metazoa with soft, unsegmented bodies, consisting of an anterior head, a dorsal visceral mass and a ventral foot. Most forms are enclosed in a protective calcareous shell. M. includes the classes Gastropoda (snails, whelks, slugs), Pelecypoda (oysters, clams, mussels), Cephalopoda (squids, octopuses), Amphineura (chitons), Scaphopoda (tooth shells), and the class of primitive metameric mollusks, Monoplacophora. [L. m., a nut with a thin shell, fr. mollis, soft]

* * *

Mol·lus·ca mə-'ləs-kə n pl a large phylum of invertebrate animals (as snails, clams, and mussels) that have a soft unsegmented body lacking segmented appendages and commonly protected by a calcareous shell

* * *

Mol·lus·ca (mo-lusґkə) [L. molluscus soft] a large phylum of invertebrates that have a soft unsegmented body often protected by a calcareous shell; it includes snails, slugs, mussels, oysters, clams, octopuses, nautiluses, squids, cuttlefish, and others.