Bivalve Shells

Coquina Blue Mussel Common Oyster

What are they?

Shells are the hard, outer casings of a large group of water-borne mollusks. Some species are snail-like in having a single, usually spiral-shaped shell, while others - the bivalves - have two shells which can be pulled together to provide a shelter for the soft-bodied mollusk to hide in. After death, only the hard shell survives and often ends up washed on the beach. With dredging and 'beach replenishment', a number of shells of deeper water species can sometimes be found on the beach, as well as the usual range of inshore species. Finding whole specimens of some species is difficult as they often get broken by the surf.


Make a note of the shape and size of the shell and carefully study the the point where the two shells join together. If the shell has ribs, the number and shape (rounded or square) of the ribs can be important. Near the point or 'beak' of the shell may be found a triangular depression. This is known as the chondrophore and in a living shellfish, it is the attachment point for a ligament. The size and shape of the chondrophore can be important for the identification of some species.

  Blue Mussel     Mytilus edulis

Up to four inches long, Blue Mussels form shoals in shallow waters or gather in dense colonies below high tide on rock pilings. They form an important food item for wintering ducks around Cape May Point and coastal inlets.
Blue Mussel Blue Mussel Blue Mussel

  Ribbed Mussel     Modiolus demissus

Up to four inches long. An abundant species of peaty saltmarshes, where this species may be found in sometimes dense and extensive colonies. Shells are usually half-buried in peaty banks and often around the roots of Smooth Cord-grass.
Ribbed Mussel

  Jingle Shell     Anomia simplex

A thin-shelled species which may grow to three inches across, but is often much smaller in size. The lower shell is decidedly brittle and has a large hole in the center, making it popular with jewelry makers, but its brittleness means it often doesn't survive the surf ride to the beach well. The shape and size of smaller individuals has earned the species the name of 'mermaid's toenails'.
Jingle Shell Jingle Shell Jingle Shell

  Common Oyster     Crassostrea virginica

A variable species which may grow up to 10 inches long, but is often much smaller - perhaps because all of the large ones have been over-harvested. A bivalve with very unequal halves; the upper shell is rugged and strongly arched while the lower half is smoother and flat. The commercial oyster species that is farmed along the bayshore.
Common Oyster Common Oyster Common Oyster

  Surf Clam     Spisula solidissima

A large clam, growing up to eight inches in width and abundant on Cape May beaches. Now that all of the best clams have been over-harvested, this species - which was once considered inferior - is by far the commonest species to end up as canned clams. Easily told by its size when full grown. Smaller specimens can be told by the substantial and easily-seen chondrophore.
Surf Clam Surf Clam

  Coquina     Donax variabilis

A small species, usually being less than one inch across. Often found in large numbers around the inlets in more turbulent waters, such as around Stone Harbor Point. Very variable in color but most often pinkish, orange, or tinged with violet; often also marked with pale rays.
Coquina Coquina

  Ponderous Ark     Noetia ponderosa

Shells up to three inches wide. A relatively large, cockle-like species with a noticeably squared shell. Note the row of small ridges just below the beak of the shell, which form a double row in the center and extend for a more or less equal distance either side of the beak.
Ponderous Ark Ponderous Ark Ponderous Ark

  Blood Ark     Anadara ovalis

Shells up to two inches wide. Similar to the Ponderous Ark but usually smaller. Note the row of small ridges just below the beak of the shell, which form a single row and extend much further one side of the beak than the other.
Blood Ark Blood Ark Blood Ark

  Bay Scallop     Aequipecten irradians

Shells up to three inches long. A relatively small scallop that is the common species found in shallow, inshore waters. Usually has 19-21 ribs and two wings at the base that are equal in size.
Bay Scallop Bay Scallop

  Stout Tagelus     Tagelus plebeius

Shells up to four inches long. Generally a bayside species, favoring sandy mud habitats.
Stout Tagelus Stout Tagelus

  Common Razor Shell     Ensis directus

Shells up to ten inches long. A common species in our area, favoring the lower intertidal zone to well below the low water mark. Often forms colonies on offshore sand bars and large winter 'wrecks' can occur when stormy seas strip out these sand bars and dump razor shells onto beaches in large numbers.
Common Razor Shell Common Razor Shell Common Razor Shell