Family Semelidae

Shell size to 6 mm; shell elongate-oval, with crowded commarginal ("concentric") ridges, beak posterior, sometimes with very fine radial threads posteriorly. Color white. These shells were first collected on Sanibel by Susan J. Hewitt on December 2014.

Shell size to 38 mm; shell thin, elliptical. Sculpture of concentric striations stronger at anterior margin, separated by wider interspaces. Concentric growth lines present between striations. Umbones posterior. Ligament internal. Color cream with strong purple or orange markings. Umbones of darker color.

Shell size to 40 mm; shell compressed, thin, orbicular. Sculpture of fine growth lines crosser by finer radial lines. Umbones almost central, pointing forward. Lunule small. Color ivory-white, internally yellow with reddish-brown or mauve speckles.

Shell size to 20 mm; shell ovate, thin, strong. Sculpture of concentric ridges and radial ribs, stronger anteriorly and posteriorly, giving cancellate aspect to shell surface in these regions. Umbones just slightly posterior. Ligament internal. Color cream or yellowish-white with reddish markings, or grayish-purple. Internally cream, white, or reddish.

Shell size to 8.5 mm; shell elongate-trigonal, with rounded ends and posterior half slightly longer than anterior, but sometimes beak is almost central. Sculpture of fine concentric ridges. Allocation of specimens collected on Sanibel to this species is tentative, as authors cannot agree with a definitive set of characters that separate this from the very similar Ervilia nitens (Montagu, 1808). The shell in the main image was collected in January 2022 by Ken Piech, on Captiva. The valves in the first supplementary image belong to a large series collected by Susan J. Hewitt at Blind Pass on Captiva, in December 2014.

Shell size to 15 mm; shell elongate, triangular, tellin-like, with dorsal margins straight. Shell sculpture of fine but well-defined growth lines. Lives in muddy-sand in sheltered, bay areas.

Shell size to 7 mm; shell small, orbicular, delicate, inflated. Surface smooth. Sculpture consisting only of fine grooves on anterior margin of right valve. Umbones pointed, small. Ligament internal. Color dull white.