The Cayenne Keyhole Limpet, Diodora cayenensis (Lamarck, 1822), is a Keyhole Limpet often found on the beaches of Sanibel and Captiva. Like most representatives of the Keyhole Limpet family, Fissurellidae, this species shows the typical keyhole-shaped orifice that serves to reroute waste water away from the head of the animal (see picture on the right). The shell has a sculpture of numerous radial riblets of which every third or fourth is larger. The animal feeds on microalgae growing on rocks or other hard substrates.
The picture of the live specimen was taken by Amy Tripp near Marco Island.