Delicate Ark

Shell size to about 25-30 mm. Shell elongate oval to quadrangular; differs from local arcids by its thin shell, with an alternating pattern of thicker and thinner radial ribs, which are in turn crossed by concentric ridges. Living delicate arks have a hairy, rich periostracum that is more abundant toward the posterior (more pointed) shell end. Shell color white, with brown periostracum. The species is known locally on Sanibel/Captiva from a few single valves found recently (illustrations, December 2015, December 2016) by Susan J. Hewitt on Turner Beach (Captiva side of Blind Pass).