Northern Moon Snail
Lunatia heros
Size: to 4"
Habitat: generally in deeper water, but possible in shallows
Notes: quite common in places
These snails are responsible for the curious sand collars that divers often find. They produce a glue to cement the sand grains together into a protective ring for their eggs.
Moon Snails are predators of other shellfish, which they smother with their enormous foot. They are themselves sometimes eaten as Scungilli.
These creatures are all of the order Gastropoda - having a single, often coiled, shell, as opposed to the bivalves, which have two matching shells. Most snails are hermaphroditic. Also, most snails have a right-hand twist to the shell, although there are exceptions.
Right:
X-ray image of a Channeled Whelk, showing internal structure.
Nudibranchs are a form of snail that has lost its shell, while Corollas and Sea Butterflies are snails that have abandoned not just their shells, but the snail-like existence entirely, swimming up into the water column as plankton.
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