The Broad-ribbed Carditid, Cardites floridanus (Conrad, 1838), is a common species on our shores. Its shell may reach about 1.5 inches in size, is very thick and relatively heavy for its size. With its sculpture of thick radial ribs, it vaguely resembles and might be confused with local species of Ark Clams. These latter, however, have a shell hinge consisting of many, small teeth that are similar in size; the Carditid, on the other hand, has a hinge with just a few teeth, all different from each other. The shell color is usually whitish with brown markings; an unusual form with yellowish color is sometimes found.
The Broad-ribbed Carditid, Cardites floridanus, from Sanibel; rare yellowish form on right. Photo by José H. Leal.