Quadrula quadrula shell description:

“Shell subrhomboid, subinflated, solid, somewhat inequilateral; beaks high and full, their sculpture doubly looped or zigzagged bars, with radial threads behind them; posterior ridge well developed, generally somewhat double, ending at the base of the shell in a feeble biangulation; in front of and behind it there is a wide, radial depression; anterior end rounded; base line incurved in front of the posterior ridge; posterior end squarely or somewhat obliquely truncated, with a sinus in the middle; at the middle of the shell or a little in front of it there is usually a wide radial swelling; surface generally more or less covered with tubercles, excepting in front of this ridge; the sculpture on this and the posterior ridge often stronger than elsewhere; epidermis greenish in young shells, greenish-brown, brown or tawny in old ones, usually somewhat shining, sometimes feebly rayed; pseudocardinals very strong, triangular, ragged; lateral of the right valve somewhat double; anterior scars well impressed; beak cavities moderately deep; nacre white, thinner and iridescent behind; pallial line deep, roughened, remote in front”(Simpson, 1914; Mather, 2007).