Shape elliptic with antero-and postero-dorsal angles. Dorsal margin and ventral margin entire. Sulcus ostial, deep. Ostium flared, triangular and cauda elongate, flexing ventrally. Colliculum raised under posterior cauda. Crista superior developed only above straight part of cauda, absent elsewhere. Crista inferior well-developed. Neck dorso-ventrally constricted. Rostrum pointed and antirostrum rounded. Excisura wide.