Pleurobema sintoxia shell description:

 “Shell generally, when adult, having the outline of a scalene or right-angled triangle, the beaks being placed at the extreme anterior point and often projecting in advance of the rest of the shell, subinflated or inflated, solid; beaks high and full, turned forward over a wide, deep lunule that passes forward under them; anterior end truncated squarely or with a  slope below and usually having a large, faint second lunule; base line nearly or quite straight; outline of dorsal slope lightly curved; posterior ridge, low rounded, ending in a rounded point at the base of the shell; median ridge very high, rounded, curved, usually separated from the posterior ridge by a radial, concave depression; surface with irregular growth lines; epidermis brown to blackish, brownish-green and rayed in young shells, scarcely subshining; pseudocardinals radial, often oblique, torn; lateral of right valve more or less double; muscle scars small, deep; beak cavities deep, compressed; nacre rose-colored or white, rarely yellowish or salmon, thinner and iridescent behind ”(Simpson, 2014; Mather, 2007).