Shell is solid, thick, inflated, mostly triangular; prominent posterior ridge drawn to a rounded point at the posterior end. Umbo is wide and raised above hinge line. Epidermis is yellowish-brown to brown; numerous green rays vary in width with spots, zigzags or most often V-shapes (chevrons); sometimes without rays. Inside shell beak cavity is moderately deep; pseudocardinal teeth are triangular, grooved and well developed; lateral teeth are short, thin, grooved and straight to slightly curved; nacre (lining) white, rarely pinkish-salmon.
Similar species: Butterfly has a flattened appearance and less developed rays. Fawnsfoot is easily confused with the deertoe, but is longer with a less prominent dorsal ridge and more distinct zigzag marks covering the shell.