There are so many sea shell types that scientists follow the system of classifying them into manageable groups. They are placed in seven classes. Gastropoda - gastropods (snails, whelks, cowries, etc.), Bivalvia - bivalves (cockles, clams, scallops etc.) Scaphopoda (tusk shells), Aplacophora (worm-like mollusks), Polyplacophora (chitons), Monoplacophora (cap-like shells bearing one plate) and Cephalopoda (nautiluses, octopuses, squids etc). Each of these classes is further subdivided into species. Most sea shells fall into the category of gastropods and bivalves. They are all from the phylum Mollusca. The following lists some of the different types of sea shells you'll find within these classes.

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Check out the basic anatomy of a sea shell on our Facts About Sea Shells page.