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New Jersey Scuba Diving


New Jersey Scuba Diving

Mollusks - Snails ( Gastropods )


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.

X-ray image of a Channeled Whelk, showing internal structure.

Gastropod anatomy

Channeled Whelk

Mollusks - Snails ( Gastropods )

Busycon canaliculatum

Size: to 8"

Habitat: intertidal down to 60 ft

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Upended and fully withdrawn, showing the operculum which closes-off the shell.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.

Northern Moon Snail

Mollusks - Snails ( Gastropods )

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.

Mud Dog Snail

Mollusks - Snails ( Gastropods )

Nassarius spp

Size: to 1"

Habitat: intertidal to shallows, on muddy bottoms


This scavenger is often found on dead fish and other animals.

Feeding Mud Dog Snails swarm over an egg mass.

Oyster Drill

Mollusks - Snails ( Gastropods )

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.

Common Periwinkle

Mollusks - Snails ( Gastropods )

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.

Atlantic Slipper Shell (Boat Shell)

Mollusks - Snails ( Gastropods )

Crepidula fornicata

Size: to 0.8 - 2 "

Habitat: attached to solid surfaces, often other larger shells


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



I make no claim as to the accuracy, validity, or appropriateness of any information found in this website. I will not be responsible for the consequences of any action that is based upon information found here. Scuba diving is an adventure sport, and as always, you alone are responsible for your own safety and well being.

Copyright © 1996-2016 Rich Galiano
unless otherwise noted



since 2016-09-11