in taxon Mollusca shell mollusc shell A calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea, many live on the land and in freshwater. UBERON:0008270 Wikipedia:Mollusc_shell