Quadrula verrucosa shell description:

"Shell large, elongated, solid, subrhomboid, scarcely inflated, inequilateral, with a decided, curved, elevated ridge, which ends well forward on the posterior base, in front of which for a long distance there is a shallow excavation; beaks low, compressed, sculptured with strong, irregular, corrugated ridges that turn up behind; surface covered as far back as the posterior ridge with irregular, different sized pustules, which sometimes form somewhat chevon-shaped [sic.] figures; behind the ridge the sculpture consists of strong, irregular, curved, corrugated and often knobbed ridges; epidermis greenish-brown, or brown, dark green in young shells; left valve with two ragged, triangular pseudocardinals and two straight laterals; right valve with one large pseudocardinal, a small one in front of it, and vestigial teeth behind it, with one lateral, which in heavy shells may be partly double; beak cavities moderately deep, compressed; anterior scars rough; posterior scars oval; nacre white, rarely purple.  In this remarkable species the male shell is obliquely truncate at the posterior base, behind the posterior ridge and ends in a somewhat blunt point considerably above the base line. From this point running towards the beaks there is generally a row of low, broad nodules or knobs that extend upward in ridges.  In the female shell this area is much smoother, and is extended into a broad, rounded wing” (Simpson, 1914; Mather, 2007).