Shell size to 50 mm; shell elongate, cylindrical. Sculpture of radial ribs and well-spaced concentric lines; sculpture stronger on anterior part of shell; anterior ribs with scale-like projections. Color white. Lives in compacted mud bottoms. Formerly in separate family Petricolidae. The supplementary image of the live animal was taken by Amy Tripp on Kice Island, Collier County, in early 2015. The image shows the incurrent (bottom) and excurrent (top) siphons, and the clam's foot (lower left). The incurrent siphon directs seawater into the animal's mantle cavity (for oxygen uptake and filter-feeding), the excurrent siphon lets used water out.