A phylum of soft-bodied invertebrates characterized by an unsegmented body differentiated into a head, a ventral muscular foot used in locomotion, and a dorsal visceral hump covered by a fold of skin – the mantle – which secretes a protective shell in many species. Respiration is by means of gills (ctenidia) or a lunglike organ and the feeding organ is a radula. Molluscs occur in marine, freshwater, and terrestrial habitats and there are six classes, including the Gastropoda (snails, slugs, limpets, etc.), Bivalvia (bivalves, e.g. mussels, oysters), and Cephalopoda (squids and octopuses).
http://www.malacsoc.org.uk/ Website of the Malacological Society of London, dedicated to the advancement of knowledge and research on molluscs
Subjects: Biological Sciences.