Shell generally similar to that of the typical L. attenuata (Deshayes) from Peru, but more robust, with relatively short and more constricted posterior incrustational appendages; superior margin of valves decidedly elevated and angulate centrally, the valves swelling out on each side of a flattened area above the hinge, where a furrow-like depression separates this portion of the valves. Antero-ventral margins of the incrustation often vertically rugose at maturity. Max. long, of holotype 71.6, of shell only 62.8, alt. at dorsal angle 23.0 mm.
Type-Locality. Outer reefs of Cholla Cove, Bahia de Adair, Sonora; Mark Rogers and Fred Wright, Dec, 1956, and Mark Rogers, Apr. 1957.