A small sample of the mix of shells on Sanibel Island's beaches. Sanibel is a beachcomber's paradise! :) It is the best beach in America and the 3rd best in the world for shells. Most of the shells are halves of bivalves since they are preyed upon by the single-shelled gastropods, crabs, sea stars and other animals.
Bivalve Navarre Beach, FL July 2008 I found this shell on the edge of the beach in the water. Although all bivalves start out life with 2 shells, most are found on the beach with just one shell because the ligament that holds them together breaks apart after they die.
It is common to find Seashells with round holes in them washed up on the beach. The animal that had been in this shell was eaten by a marine snail. These snails have a rasping mouthpart called a radula which can drill through the hard shell.
