Outer shell is large, thick, and elongated to suboval; very inflated. Unbo is swollen and elevated above hinge line. Epidermis is shiny, light tan to light green or brown; becomes black to greenish black with age; young often with faint green rays. Broad beak cavity; teeth absent; nacre (lining) iridescent and variable, often silvery-white, tinged with pink or salmon.
Similar species: Flat floater is more circular and its umbo is almost flush to the hinge line. Paper pondshell has a thinner shell and a flatter umbo.