Shape trapezoidal with postero-dorsal angle and convex medial face and slightly concave lateral face. Dorsal depression shallow, along crista superior. Dorsal margin and ventral margin crenate. Sulcus ostial, deep. Ostium flared and cauda elongate, markedly flexed and bulbous at posterior. Colliculum large in ostium. Collum raised, largely wall-like. Crista superior ridge-like anterior to caudal flexion and absent after caudal flexion. Crista inferior well-developed. Neck dorso-ventrally constricted. Rostrum extended, rounded. Excisura wide. Notch deep.