L. undata. The waved Lucina.
Orbicular, thin, convex, undulated with fine irregular striæ; exterior pale yellow, interior white; margin glossy and plain.
8. Donax. The Wedge Shell. Twenty-seven species.
The singularity of form that gave rise to its common name renders it easily distinguished. It very much resembles a wedge, being very broad and thick at one extremity, and gradually tapering towards the other. They vary in colour, but the most general is purple radiated on a white ground, diverging from the beak to the margin; many have an orange tinge, and others a pink hue; the interior generally partakes of the colour of the exterior. There are not, perhaps, two species that have absolutely the same hinge.
The Donax is found buried deep in the sand of the seashore, with the short side uppermost.
Shell sub-trigonal, greater in length than in height, equivalve, very inequilateral; posterior side much shorter than the anterior; summits almost vertical; hinge complex, similar; two cardinal teeth in one or both valves; one or two remote lateral teeth on each valve; ligament posterior, short, and inflated; two rounded muscular impressions.
Donax scortum.
D. pubescens.
D. compressa.
D. cuneata.