Family Mytilidae

Shel size to 18 mm; shell elliptical, externally sculpted with concentric ridges. Beaks rolled inward. Periostracum grayish-brown. This species is a borer living in dead shells and small coral heads. The shell illustrated was collected within a Kitten Paw, Plicatula gibbosa, shell. From the East End of Sanibel Island, Florida, by Jim Scatterday.

Shell size to 40 mm; shell very thin, fragile, elongate, tapering gradually toward posterior end. Sculpture of fine concentric growth lines. Surface glossy. Hinge with no teeth. Ligament thin, small. Periostracum thin, green. Color light-gray. Inner surface nacreous. Found in mud in protected bay areas.