Distinguished from the Mya by the prominency of the apex and the
situation of the ligament.
Shell regular, elongated oval, gaping at the two extremities, equivalve,
inequilateral; summit but little marked, and anterodorsal; hinge very
complete, similar, formed by a conical primary tooth before a short,
compressed, ascending callosity; ligament exterior, attached to the
callosity; two muscular impressions.
_P. Aldrovandi._ The Panopæa of Aldrovandus. Pl. 5, fig. 2.
The type of this genus, transversely elongated, undulated;
concentrically wrinkled; of dark green colour, almost black.