Fusconaia flava shell description:

 “Shell quadrate to triangular; dorsal line short, straight only at the hinge; sharply angled posteriorly; ventral line straight, anterior end with a straight face dorsally, gently rounded ventrally; posterior end sharply truncated above, sharply rounded below.  A broad, shallow sulcus anterior to the posterior ridge; shell is strong and heavy even in small shells; in old shells the valves usually become quite thick in the anterior half; size to 9.5cm; moderately inflated, posterior ridge prominent, sometimes sharply angled dorsally, often flattening ventrally and causing a double angle on the postero-ventral margin.  Beaks broad, raised above the hinge line, inequipartite; beak sculpture consists of three to five faint concentric bars that become sharp-angled on the posterior slope and may form slight tubercles there.  Growth lines often prominent, forming raised concentric ridges which are dark-stained at rest periods.  Epidermis yellow-brown in young, becoming chestnut brown to black when old; small valves may have faint green rays on the umbones. Left valve has two dissimilar pseudocardinal teeth; the anterior one is narrow and elongate, the posterior one heavy and triangular, both are rough and serrated; the two lateral teeth are short and straight.  Right valve has one heavy, serrate pseudocardinal tooth; the single lateral is short, nearly straight and stout; sometimes a smaller tooth develops ventrally to the main tooth.  Interdentum well to poorly developed; beak cavities deep and fairly broad; nacre white, sometimes tinged with salmon or pink, iridescent posteriorly” (Mather, 2007).