Mollusca

Caudofoveata
Aplacophora
Polyplacophora
Monoplacophora
Bivalvia
Scaphopoda
Gastropoda
Cephalopoda
† Rostroconchia
† Helcionelloida
† ?Bellerophontida

The molluscs (British spelling) or mollusks (American spelling) are members of the large and diverse phylum Mollusca, which includes a variety of familiar animals well-known for their decorative shells or as seafood. These range from minute snails and clams to larger organisms such as squid, cuttlefish and octopus, (these latter organisms are among the most neurologically-advanced invertebrates). There are some 112,000 species within this phylum. The scientific study of molluscs is called malacology.

The vast majority of molluscs live in marine environments, and are found intertidally, in the shallow subtidal and on the continental shelf, although some species do live in the abyssal depths of the oceans around hot vents. Not all mollusks are marine: two groups, the bivalves and the gastropods, also contain freshwater species. Only the gastropods have representatives that live on land: the land snails and slugs.