Shape elliptic with convex medial face and concave lateral face. Dorsal margin and ventral margin serrate. Sulcus ostial, deep. Ostium flared and cauda elongate, flexed ventrally at posterior tip. Colliculum low and large in ostium, extended over excisura. Crista superior and crista inferior well-developed. Neck dorso-ventrally constricted. Rostrum blunt, rounded, downward. Excisura wide. Notch shallow.