The Broad-Ribbed Cardita might be mistaken for an Ark Shell (Family Arcidae), but actually Carditamera floridana is a member of Family Carditidae. The adult bivalve is approximately 1½ inches long. The shell is sturdy, bluntly oval, and has about 20 robust radiating ribs. The ribs are wide, beaded or scaly, and have purple or reddish-brown spots scattered over them in somewhat concentric bands. The background color of the shell is white, grayish, or slightly yellowish. Old Carditas may have lost their markings. Fresh specimens sport a gray periostracum. The inside of this type of clam shell is porcelain-white.