La Union, Gulf of Fonseca, San Salvador (Lowe, 1931). Type 155503 ANSI*.; paratypes in Lowe collection.
The shell is thin, short and high, with a weakly convex left and flat right valve; white. Upper margin is concave behind the beaks; basal margin strongly convex in the middle and posteriorly; anterior third contracted, rounded in front. Sculpture of many narrow radiating riblets on the posterior two-thirds, much weaker in the right valve. Anterior third with lines of growth only. There is also some very weak, coarse, concentric cor¬rugation of both valves. Teeth rather well developed but thin.
Length 24.5 mm., height 20.7 mm., diam. 4.0 mm
This species has about the outline of P. grandis and appears quite unlike any species described from the Panamic province.