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.
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.
Right:
X-ray image of a Channeled Whelk, showing internal structure.
Gastropod anatomy
Busycon canaliculatum
Size: to 8"
Habitat: intertidal down to 60 ft
Notes:
Whelks are the largest snails in this area. Related Lightning Whelk grows to 16", and is sometimes called Conch and eaten as such. Whelks prey on bivalves by drilling through their shells.
A large ( and filthy ) whelk feeding on something. The head end is to the left.
Upended and fully withdrawn, showing the operculum which closes-off the shell. This
individual was about the size of your hand. Note the curious puffer fish at upper-right.
The somewhat smaller Waved Whelk Buccinum undatum is a scavenger
See Restrictions and Health Advisories for catch limits.
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.
Nassarius spp
Size: to 1"
Habitat: intertidal to shallows, on muddy bottoms
Notes:
This scavenger is often found on dead fish and other animals.
Feeding Mud Dog Snails swarm over an egg mass.
Urosalpinx cinera
Size: to 1"
Habitat: subtidal down to 50 ft
Notes: This little snail uses acid and its rasp-like tongue to drill a neat hole in a bivalve or barnacle victim, then sucks out the contents.
Littorina littorea
Size: to 1.2"
Habitat: intertidal, on any solid substrate
Notes: vegetarian - feeds on seaweeds
This is another good snail for a cold-water aquarium, as it will constantly clean all surfaces of algae, and also consume any other waste it finds. They are also edible.
Crepidula fornicata
Size: to 0.8 - 2 "
Habitat: attached to solid surfaces, often other larger shells
Notes:
Although the dead empty shells superficially resemble bivalves, Slipper Shells are actually extremely flattened snails. The living animal has only a single uncoiled shell, and lives under it attached to a hard surface. A small shelf inside gives these odd animals their name. The illustration shows the shell from above on the left and from below on the right. Slipper shells are quite commonly attached to the undersides of Sea Scallops, often in stacks. Filter feeders.
Slipper shells hitching a ride on a scallop
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Copyright © 1996-2008 Rich Galiano
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