Disc broad and short; snout strongly notched medially to form two lobes; head relatively narrow, its width across middle of eye 6.7–7.4 in DW; cephalic lobe posterior edge not (or just) reaching mouth; tail long, usually 2.4–3.4 times disc length (when undamaged); dorsal fin origin distinctly behind pectoral fin insertions; posterior margin of dorsal fin strongly concave; sting (when present) behind dorsal fin free rear tip. Body colour disc plain greenish brown to blackish above, white below; tail base white below remainder of tail black.