Shells are ovate, slightly inequilateral, and strongly convex. Sculpture consists of fine concentric ribs. Valves are strongly inequivalve (one valve larger than other).

Size: 5-10 mm.

Ecology: inhabits shallow-offshore marine (10-100 m) waters, burrowing in silt near the sediment surface.

Geological range: Late Miocene-Late Pliocene (11-3 million years ago).

Geographic distribution: Caribbean – Panama and Costa Rica.