« Shell oblong, elevated, solid. Valves regularly arched, the lateral areas very strongly raised, coarsely sculptured. The median areas of the valves are sculptured with longitudinal lirae, which are granulous and anastomose or branch irregularly. The head valve has strong concentric ridges, 7 to 10 in number in adults, the intervals being finely pitted or granose. The lateral areas of the intermediate valves are very much raised, and sculptured with concentric ridges like the head valve. The posterior valve is very solid and thick, its apex posterior but recurved forward and much elevated ; its posterior slope is subvertical, convex, terraced. The sutural plates are triangular and stout ; the jugal sinus rather narrow. Insertion plates are completely lacking. It is lusterless, and light buff in color. Girdle very narrow and thin, bearing most minute, close delicate deciduous scales. »