Diagnosis. Ventral sucking disk absent. Nostrils single (one on each side of snout). Pseudobranch absent. Teeth almost always simple, occasionally with small shoulders, rarely trilobed. Pectoral fins usually notched, often deeply, forming lower and upper lobes, usually with fewer rays than in anal fin. Pectoral radials 4, 3, or 2. Pleural ribs absent. Caudal fin rays usually fewer than 10, procurrent rays usually absent but occasionally one ray present. Vertebrae 51 –about 81.
Distribution. At least 80 species in the Southern Hemisphere, known from Australia, east and west coasts of South America, Falkland Islands, southern Africa, and Antarctica. Four species known from New Zealand waters (Fig. 17).