Most of the interior of the valve is pale but the margins are dark. The line separating the two is the pallial line (Fig 1). It is the line of attachment of the mantle to the valve.
A small anterior adductor muscle scar can be seen at the anterior end of the valve (Fig 1). It lies on the pallial line on the ventral edge of the valve. The much larger posterior adductor muscle scar is located at the posterior end, displaced to the dorsal side. These scars mark the sites of attachment of the adductor muscles to the valves.
The scar of the anterior pedal-byssal retractor muscle is a small, pale, slender, elongate depression under the overhang of the anterior edge of the valve below the ligament (Fig 1). The scar of the posterior pedal-byssal retractor muscle is a large, lobed, narrow, dark area extending anteriorly from the dorsal edge of the posterior adductor scar.