Lateral Mussel

Shell size to 9 mm; shell small for family, elongate-ovate, inflated, thin-walled, with taller section on posterior one third. Umbo poorly defined. Two slanted lines divide valve in three areas: a smooth central one, anterior and posterior areas with strong radial ribs. Color greenish-brown, but central area of lighter color. Inner nacreous layer very thin, translucent.