Disc oval to roughly diamond-shaped, broader than long; front-side margins of disc nearly straight; snout pointed, very slightly projecting; tail slightly longer than length of disc; tail fin absent, but fin folds on upper and lower surface of tail, upper fold short and low, lower fold longer and deeper, both folds end abruptly at the same place on the taill; upper surface of disc mainly smooth except for a long central row of thorns on back and base of tail, that is flanked on each side by short row of thorns or spines on middle of disc.
Generally dark brown or blackish without distinctive markings.
Maximum length, 180 cm (disc width 122 cm).
Inhabits sand-mud bottoms.
Depth: 0-70 m.
Southern California to Peru, the Revillagigedos, the Galapagos.