Goniobasis virginica
Size: to 1"
Habitat: flowing water
Notes: This is one example of the many small snails you may find during a freshwater dive. They are very common in Round Valley Reservoir, which is filled from the Raritan River.
This page lumps together representatives from crustaceans and mollusks. Freshwater typically has lower diversity than the ocean. However, this is just a tiny sample of what may be found.
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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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