The height of the shell is approximately half the total length. The lower margin of the shell is often markedly curved all over its length. More seldom is this curved shape less pronounced. The lower margin bends softly up to the posterior end, that often is wedge-shaped.
Older specimens are often dark brown.
The species can be very thick shelled in running water. The umbonal rugae consist of two irregular radiating rows of elongated wavy tubercles, some of which join up to form undulating ridges. The anterior adductor muscular impression is not situated so close to the anterior end as is seen in the Painter s mussel. Fairly powerful hinge-teeth are present. In the right valve the anterior lateral and cardinal teeth are well developed, thin and wedge-shaped.