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Molluscs Snails | Clams and Mussels | Amphineura | Tusk Shells
Their diversification has led to an extremely varied set of body plans and lifestyles, from completely armoured and virtually immobile filter-feeding clams to jetting carnivorous squids. Molluscs originally had shells, but many groups have now severely reduced or lost them, usually as they became more mobile. They are the largest, fastest, and smartest invertebrates. One hundred and ten thousand species of molluscs exist today in seven classes: Cephalopoda (octopi, squids, nautilus and cuttlefish), Bivalvia (clams and mussels), Gastropoda (snails and slugs), Polyplacophora (chitons), Aplacophora, Monoplacophora, and Scaphopoda (tusk shells). Canada has 1 500 species, mostly gastropods and bivalves.
Order Mesogastropoda
Order Basommatophora
Order Archaeogastropoda Order Neogastropoda
Clams and Mussels (class Pelecypoda) Order Eulamellibranchia
Order Neoloricata
Tusk Shells (class Scaphopoda) Order Gadilida
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The
Mollusca are an ancient group, arising over half a billion years ago and
dominated the oceans before the coming of fish. They soon diversified
and now include some of the best-known invertebrates: clams, snails, slugs,
squids and octopi are all molluscs. 