Appearance
Ortmanniana ligamentina is a large species of mussel, with adults reaching up to 140 mm (5.5 in) long. The stout shell may be oval, oblong, or elliptical in shape. The anterior end of the shell is broadly rounded, while the posterior end may be broadly rounded or somewhat pointed. The periostracum is light yellowish brown to greenish in color, becoming dark brown or dull olive yellow with age. The periostracum may also exhibit broad, interrupted or uninterrupted dark green rays, though these are not present in all specimens. The external surface of the shell is relatively smooth but often marked with irregular raised concentric ridges. The nacre is white, becoming iridescent towards the posterior end of the shell.

