A relatively common species in the tropical western Atlantic, the Twin Drupe, Trachypollia didyma (Schwengel, 1943), is a small (about 15 mm, or 0.6 inch) muricid gastropod that grows from a free-living, pelagic larva into a crawling adult. The larval shell is preserved on the apex of the adult shell as its protoconch. The images show, clockwise from left, a young shell (about 4 mm, or 0.16 inch) captured under a scanning electron microscope (SEM); in color, an adult shell measuring about 12 mm (about 0.5 inch), and a detail showing the protoconch, also under SEM. All images by José H. Leal. Learn more about mollusks and their shells at the Museum's Southwest Florida Shell Guide.