Donax variabilis Say, 1822
Wedge (or Bean) clams are found in the sand of almost every tropical or temperate beach around the world. The Atlantic Coquina, Donax variabilis, is found on beaches in the Southeastern United States. The clam is no longer than half of an inch. Twin siphons extend from the two hinged shells which form the bivalve. (These siphons look like snorkels.) One of the siphons takes in oxygen- and food-bearing water; the other pumps out oxygen and wastes. The mollusk also has a “foot” (actually the underside of its body) which it extends in order to dig or rest in the soft sand.
The animal lives in colonies just below the surface of the sand in the littoral zone (the area along the store which is usually exposed to the sun twice a day due to tides). Deposits of old shells, cemented by their own lime (calcium carbonate) compacted over time, create a limestone soft enough to be cut with a saw. (The shells of all mollusks are formed from lime which they extract from the sea.) This marine limestone can be used as a building material.
The little living clams burrow into the sand at the edge of the surf and are “unearthed” by the action of the waves. This is nature's plan, for each wave brings nourishment to the Coquina. They position themselves in the best place for maximum exposure, following the direction (incoming or outgoing) of each wave wash.
Gathered alive, the clams can be made into a seafood broth. Rinse them very well; place in a pot with enough cold water to almost cover the shells; bring to a boil; reduce heat and simmer a few minutes, stirring a couple of times. Drain off the broth (this is the part you eat!) and serve immediately, enhanced with a little cream or butter if desired. No salt is needed. The broth can also be served chilled.
From the point of view of shell collectors, Donax variabilis is a treasure because of the beautiful colors and markings on the shell. Some of the shells have rays of color extending from the beak and hinge areas, making the shell look like a Southern sunrise.
A shell may have concentric bands of color running the length of the shell; or it may have both rays and bands. The colors are fabulous: yellow, rose, pink, pale blue, lavender, tan, brown, and orange. Often the inside of Donax variabilis is deep purple.
One might find shell halves, intact closed-up shells, or shells spread out, butterfly fashion. In fact, a common name for the Coquina is Butterfly Shell. They are sometimes also called Pompanos or, as I already mentioned, Wedge Shells.