Cardita Seashells

Cardita seashells found on beaches were the homes of Cardita clams. The clams live just off shore buried in the sand or mud from 3 to 25 feet deep. In Florida, the variant Carditamera floridana, are a common sight on both the Atlantic and Gulf sides. They are most commonly found as half of the bivalve seashell. 

Cardita seashells can grow up to 1 ½ inches long in a somewhat oval shape. Their width is about half of the length at the hinge area. If you put 2 similar size seashells together to form a “clam”, they are about as high as they are wide. 

They have deep pockets inside the seashells and are generally white on the inside. Some bleed thru of the outside color, especially the darker ones, can be seen on inside of the some cardita seashells. Of course, the seashells found up on the beach have been unoccupied for a while and acted upon by water, wind, and sand. This most definitely will affect their looks. 

Colors can range from an almond white to a chocolate brown with a few grays thrown into the mix. The colors are found on the highly defined ribs on the cardita seashells’ surfaces in the form of “dots.” The ribs, anywhere from 15 to 20 of them, can add quite of bit of texture and radiate from the hinge area out to the edge. These ribs give the Cardita seashells another of their common names, the broad-ribbed carditas. 

The clams that make the Cardita seashells feed by filtering plankton and other organics bits from the water that flows over them. The older they are the larger they grow their seashells until they reach their maximum size/age. 

They are prolific breeders, reproducing during the summer by releasing eggs and sperm into the water when spawning. The fertilized eggs develop into larvae that float around for a few weeks. 

The survivors eventually float down to the seabed and bury themselves in the sand or mud. There they attach themselves by means of “threads” and keep eating plankton and other small bits, growing themselves and their homes. 

Many of them fall prey to the predators of the sea, which include other mollusks such as conch and whelks. Seabirds and other animals also feed on the soft insides of the Cardita clams. Their homes then become empty and can be pushed up on our beaches for us to find during our visits to the beach. 

These seashells are very useful in seashell arts and crafts. Wherever they are used in shell crafts, they can add a bit of color and texture. For ideas on using them and other seashells in shell crafts visit  Shellcraft Guides. 

For more information on the Cardita clams do a search. Try Carditamera floridana, Florida Cardita, and broad-ribbed carditas as search terms as see what you can find.