American Tusk Shell

Shell size to 25 mm (usually under 20 mm); shell tubular, dull, chalky, or glossy. Six ribs evenly spaced, but with occasional seventh rib randomly placed. There is variation in relative width of intercostal (between ribs) spaces; with small longitudinal riblets usually present. Apex (narrow end) hexagonal in cross-section. Aperture hexagonal in immature specimens, and hexagonal to circular in adult specimens. Curvature variable, but not extremely pronounced. Most abundant tusk shell species found on Sanibel. Color white. The illustration shows an adult shell on top, its aperture on left and apex on right. Center image is of a juvenile shell, its aperture below. (Entry prepared in cooperation with Rebecca Mensch.)