Humpback smooth-hound the lower ones. The teeth have a main pointed cusp and sometimes smaller subsidiary ones. The first dorsal fin is approximately triangular and the trailing edge is fringed with bare, dark-coloured collagen rods known as ceratotrichia. The pectoral fins are large and the pelvic fins moderately so. The caudal peduncle is short and the lower lobe of the tail fin is hardly curved in adults. The colour of this shark is plain grey or greyish-brown without any spots or barring. The humpback smooth-hound is found in the eastern Pacific Ocean off the coast of Peru and Chile, between 1°N and
Slender smooth-hound about one-sixth of the total length; the lower caudal fin lobe is indistinct, while the upper lobe has a strong ventral notch near the tip. The skin is densely covered by small, overlapping dermal denticles. The crown of each denticle is mounted on a short stalk and bears three horizontal ridges leading to marginal blade-like teeth, with the central tooth particularly long. This species is plain brownish-gray above and lighter below. It grows up to long and in weight, with females reaching a slightly larger size than males. The slender smooth-hound is likely a schooling species. It preys on a