• José H. Leal

Shell of the Week: The Horse Conch

Triplofusus giganteus (Kiener, 1840), one of the most iconic local marine snails, is well know for its very large size. It grows to about 60 cm (24 inches) in length, and is the second largest gastropod in the world, second only to the Australian Trumpet, Syrinx aruanus (Linnaeus, 1758), which reaches 910 mm (36 inches). We are all familiar with the large Horse Conch shells, but very few know how a young Horse Conch shell looks like. In the illustration, I included a 12 mm (about 0.5 inch) young shell for comparison (bottom right). The white part on top, known as the protoconch, was manufactured by the snail while still inside the egg capsule, prior to hatching. As indicated in the top-right image, in well-preserved shells the young shell remains at the shell apex. That small Horse Conch shell was collected in the early 1990s on Sanibel, by Marjorie Lloyd.

The Horse Conch, Triplofusus giganteus. Clockwise from left, adult shell, detail of shell apex, young shell. Photos by José H. Leal.