Shell rhomboidal, with right and left valves of equal size and shape (equivalve) or with a distorted plane of commissure (slightly inequivalve); umbones anterior and pointing to the anterior end of the shell (prosogyrous); maximum shell inflation coinciding with a faint diagonal ridge (carina); antero-dorsal, postero-dorsal and posterior margins straigh; anterior and ventral margins rounded; lunule faintly marked by a shallow groove in juvenile specimens, indistinct in adults; lunular area flush with the general surface of the shell; escutcheon narrow, shallowly sunken; shell exterior yellowish to pale brown, with brown chevron patterns (tent marks) and rays; external sculpture of commarginal ridges, narrower and higher at the posterior and anterior ends of the shell; umbonal area smooth; internal surface of the shell usually without pigmentation, sometimes with a yellowish or orange blotch extending from the umbonal cavity to the pallial line; internal shell margins without crenulation; pallial sinus present, extending anteriorly as far as the posterior end of the ligament; ligament external, long, extending for more than half the length of the postero-dorsal margin, supported by a nymphal ridge in each valve; hinge of the right valve with three cardinal teeth (3a, 1 and 3b) and a faint posterior lateral (P1); middle and posterior cardinals (1 and 3b) subdivided distally (bifid); hinge of the left valve with three cardinal teeth (2a, 2b and 4b); middle cardinal tooth (2b) subdivided deeply, giving the impression that four cardinal teeth are present in total in the left valve.
Original description, by Linnaeus (1758, p. 689):
"V. testa ovata antice angulata striis transversis.
Bonan. recr. 1. f. 67.
Rumph. muf. t. 43. f. B. Chama literata oblonga.
Gualt. test. t. 86. f. E. F.
Argenv. conch. t. 24. f. A.
Kratzenst. Regens. 16: t. 4, f. 39.
Habitat in Europa australi & India.
Color saepe cinerascens, sed plurimum varians; saepiusque characteribus notatus; variat etiam rugis antice longitudinalibus, in majoribus imprimis & indisis."