Gouldia costaricensis
Original description by Olsson (1922, p. 234):
"Shell small, high, rounded trigonal, moderately convex; beaks small and pointed slightly forward, in young shell nearly central but becoming vvith maturity slightly anterior; anterior and posterior extremities nearly similar and evenly rounded; surface with fine, concentric lines, most distinct and even towards the ventral margin, and with faint, radial striae on the anterior and posterior slopes; lunule large, lanceolate, defined by an impressed line; interior of shell deep, with a concentrically grooved margin.
Length 4.85, height 4.75, diameter of right valve 1.50 mm.
The Costa Rican shells differ from the typical altum, described by Dall from the Oak Grove sands of Florida, in being more trigonal in form and with higher beaks. The sculpture of its surface is mainly concentric, the radials showing only as very faint striae on the posterior and anterior extremities.
Gatun Stage: Middle creek.
Coll. 6, Estrella River."