Shell is thick, inflated, elongate with a pointed posterior end. Umbo is low and broadly rounded. Epidermis is shiny; younger mussels yellowish-green with fine green rays; adults straw-colored with faint or no rays, becomes darker with age. Inside shell beak cavity is moderately deep; pseudocardinal teeth thin, elongate, serrate and well-developed; lateral teeth long and straight to slightly curved; nacre (lining) white.
Similar species: Black sandshell has a very dark epidermis. Fatmucket shell is not as elongate and more inflated, typically with prominent rays.