The shell is narrowly elongated and triangular in shape, with the umbo at the pointed anterior end. It is rounded at the pos terior end, moderately inflated, smooth, not gaping, with an adherent periostracum varying from dark blue or purple to brown. Generally 2-4 in (5-10 cm) in length, the largest reaching 8 in (20 cm). Shell shape and size influenced by environment, especially tidal level, habitat type, and population density. Interior is faintly nacreous (pearly). Soft body secretes strong stalk of byssal threads exiting shell at ventral margin; mantle edge is yellowish brown; anterior adductor muscle narrow and elongated.
Was this article helpful?