Shape elliptic to oblong with convex medial face and concave lateral face. Dorsal margin and ventral margin serrate. Sulcus ostial, deep. Ostium oblong, bended downward and cauda elongate, flexed ventrally at posterior. Colliculum low and large in ostium. Crista superior and crista inferior well-developed. Neck dorso-ventrally constricted. Rostrum pointed, large, downward. Excisura wide. Notch deep.