Gasconsia Northrop, 1939

 Large to very large (up to 120 mm in width), semi elliptical, gently to strongly biconvex shell; cardinal margin wide and cardinal extremities round. Ornament of concentric growth lines and some stronger ribs. Ventral valve with muscle field platform. Dorsal interiors with rounded dorsal sockets, pair of central muscle scars, and two larger anterior muscle scars with welldeveloped anterior lateral directed ridges.