Size

Cardita clams can grow to be about 1 inch (2.5 cm) wide and near 1 1/2 inches long.  Their shells have a slight oval shape. Two halves together form a shape that is somewhat heart shaped, and nearly as high as they are wide.

Like most clam seashells I have seen, the widest part of their shell is at the hinge point. The shells are fairly deep on the inside, leaving plenty of room for the mollusk whose home they were.

Color, Pattern & Texture

The Cardita seashells I have picked up on the beach range in color from a milk chocolate brown to a light almond, with an occasional gray/black thrown in. Articles I’ve read do not mention grays and blacks, so these colors may be due to other influences such as oil or tar ball pollution.

Unless worn by sea and sand, the seashells have widely spaced ribs that radiate from the hinge area to the outer edges of the shells. The coloring is almost always located on these ribs, and look like a lot of dots with the underlying shell color showing in-between. Although the most common underlying color is white, they can also be found with the coloring to be somewhat gray or a bit yellowish.

The inside of the seashells are mostly white. Some seashells exhibit color bleed through near the outside edge, usually looking like a dark band when looked at from the inside.

Habitat

Cardita clams live off the coast in waters from 3 to 25 feet deep. They bury themselves into the sand or the mud, and hold themselves in place using threadlike filaments. They range from Florida’s east coast to the beaches of the Gulf of Mexico.

Feeding

Like many clams, Cardita clams feed by filtering plankton out of the water that flows over them. Any organic bits are filtered out and digested. The waste is then added back into the water.

Lifespan & Breeding

The Cardita clam is a prey species. It seems like everything in the ocean wants to eat it. Predator snails like conch and whelks consume them, as well as other sea predators such as the octopus. The trick is to get into the relatively thick seashell of the Cardita in order to consume the soft animal inside.

Cardita clams reproduce by letting loose sperm and eggs into the water to fertilize. Usually, the water needs to be at a warmer temperature so spawning takes place during the warmer part of the year. Like all prey species, they release an overabundance of eggs and sperm into the water, since many of them will be lost to predation.

The fertilized eggs hatch into larva. These larvae float around in the waters eating plankton. After 3 to 4 weeks, the survivors move toward the bottom , burrow in, and start the cycle all over again.

Alias

The actual name for these clams is “Carditamera floridana.” Their common name is the Florida Cardita. They are also known as the broad-ribbed cardita clams. 

Shell Crafts

These seashells are very useful in seashell arts and crafts. They can be used to create art on magnets, jars, plaques, and photo frames (see Shellcraft Guides for ideas). They can also be used on beach, reef, and seafloor sculptures.

Wherever they are used in shell crafts, they can add a bit of color. The broad ribs also add texture. I find them very useful in my seashell art.