Stimpson Chimney Clam, Rocellaria stimpsoni Tryon, 1861, is a small bivalve that measures about 18 mm (3/4 inch). Chimney clams bore into calcareous substrates such as coral and shells, where they form bottle-shaped dwellings of calcium carbonate (same material as shells). Found locally in valves of Cross-Barred Venus clams (center of image), Ponderous Arks (right), Quahogs, Jewel Boxes, and other bivalve and gastropod shells. In some extreme cases, the bivalve will form dwellings independent of the host shell, agglutinating small bits of shells and other debris. The species had been forgotten locally for many decades, and was re-discovered on Sanibel by local resident and Shell Museum friend and volunteer Dr. James Scatterday.
Stimpson Chimney Clam (left), Cross-Barred Venus shell with Chimney Clam dwelling (center), and Ponderous Ark shell showing position of embedded Chimney Clam (right).