Dysnomia penita Conrad, 1834 Epioblasma penita, the southern combshell or penitent mussel, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.

The shell of the mussel in a variety of colors including yellow, green, orange-brown, and black.

It has a squarish shape with irregular growth lines and has a radially sculpted posterior.

The inside of the shell is white and somewhat iridescent.

Because the species is sexually dimorphic, female southern combshells have an expanded posterior shell.