Thick, squared to rounded shell and slightly inflated with two rows of pustules (bumps) radiating from the umbo to the shell margin and separated by a sulcus (smooth depression); anterior portion is usually smooth. Small, slightly raised umbo above hinge line. Epidermis is yellowish-green with faint rays in juveniles; darkens with age to medium to dark greenish-brown or brown. Inside shell beak cavity deep; pseudocardinal teeth serrate and well developed; lateral teeth long and straight; nacre (lining) white, iridescent posteriorly.
Similar species: Wartyback and pimpleback do not have a depression and are more rounded. Purple wartyback is generally more compressed and has purple nacre. Monkeyface has a row of knobs instead of a depression.