Shell thick, equivalve, inequilateral, with a sculpture made of thin to thick radial costae separated from each other by grooves of same strength, to which are corresponding the marginal crenulations that are especially noticeable inside the valves; hinge: absence of anterior laminar teeth (Pérez, 2019).
 

Shell very inequilateral, suborbicular to transverse, slightly gaping ventrally, with an anterior side short and a posterior side lengthened; sculpture of imbricated or squamose costae crossed by weaker growth marks; hinge small; ligament external, opisthodetic.
 

Shell moderately inequilateral, subtriangular; sculpture of large squamose radials separated from each other by thinner grooves; hinge: no anterior cardinal tooth on the right valve, laterals obsolete.
 

Shell subquadrate, inequilateral; posterodorsal margin angular, posteroventral margin rounded; sculpture of sharp scaly radial ribs separated from each other by large interspaces.
 

Shell small, inequilateral, subtriangular; sculpture of numerous thin radials crossed by commarginal ribs of about equal strength; the radials become wider towards the anterior side, the commarginals stronger around the summits.
 

Shell inequilateral, quadrate, convex; posterodorsal margin angular, posteroventral margin rounded; sculpture of squamose radial costae separated by thinner interspaces; the costae become more scaly or squamose near the margins, especially on the posterior side.