The black mudalia is a small species of aquatic snail growing to 13 millimeters (mm) (0.5 inches) in length. The shell is thin, ovately conic in shape, smooth, and the top of the shell is usually eroded. The shell color is green to brown, occasionally with brown transverse color bands. In the wild, however, the shell is almost always covered with black mineral deposits. The operculum (hard structure that covers the aperture when the snail body is drawn into the shell) is thin, dark, oval, and impressed at occasional growth lines.