Incongruous ark

Scapharca brasiliana

Family Arcidae - arks

Bivalve (2 shells); shell ovoid, slightly triangular in shape, anterior end bluntly rounded, posterior end more angular; beaks large, separated (not touching) when view from the side, hinge line (edges between beaks) straight on top, slightly curved below; ligature area beneath beak (externally) triangular shaped; shell color white, brown furry covering (periostracum) when alive; heavily beaded radiating ribs on left valve, right valve has smooth radiating ribs, beaded only on anterior and posterior ends; beads somewhat elongate (wider than tall); smooth radiating ribs on internal surface; edges of shell crenate (scalloped); left valve overlaps right valve; comb-like teeth on interior of hinge line, teeth becoming smaller towards the center; ventral edge of left shell curved slightly outward when viewed from the ventral side.
Similar Species
The incongruous ark is most similar to the triangular ark. The triangular ark has beads that are not as oblong (except possibly on sides) and the shell has a straight ventral anterior edge.
Gulf and bay, sandy bottoms
Maximum Size
6.2 cm (2 1/2 in)
Other Common Names
Previous Scientific Names
Anadara brasiliana