which lack nictitating membranes. The mouth forms a broad arch, with very short furrows at the corners. There are 21–25 and 20–27 tooth rows in the upper and lower jaws respectively. The knife-like teeth each have a strongly angled main cusp flanked by up to three smaller cusplets on either side; the lateral cusplets are absent in young sharks. There are five pairs of gill slits, with the fifth pair the longest. The lateral line runs along each side of body in a conspicuous furrow. The pectoral fins are short, while the pelvic fins are relatively large with long bases. The first dorsal fin is small and originates at or behind the level of the pelvic fin origins; the second dorsal fin is similar to the first and positioned close behind. The anal fin is absent, and the stout caudal peduncle lacks depressions at the caudal fin origins. The caudal fin has a longer upper lobe without a notch in the trailing margin, and an indistinct lower lobe. The skin has a dense, uniform covering of non-overlapping dermal denticles measuring up to across, which are never fused together as in the bramble shark. Each denticle is thorn-like, with strong ridges running down the central spine and radiating out over the star-shaped base. The denticles beneath the snout are very fine in adults. The prickly shark is plain brown or gray, often with a purplish tint, and has black trailing margins on the fins. The underside is paler, most obviously on the snout and around the mouth. It may reach a length of . The maximum recorded weight is for a long female. Distribution and habitat The prickly shark is widely distributed around the Pacific Ocean. In the western and central Pacific, it has been reported off Japan, Taiwan, Victoria and Queensland in Australia, and New Zealand, as well as around the islands of Palau, New Caledonia, Tonga, Hawaii, and possibly the Gilberts. In the eastern Pacific, it is known to occur from Oregon to El Salvador (including the Gulf of California), around the Cocos and Galapagos Islands, and off Peru and Chile. This species generally seems to be uncommon; an exception is in Monterey Canyon off California, where sharks of both sexes are abundant throughout the year. Favoring cooler temperatures of , the prickly shark is mostly found below depths of , particularly in the tropics. It has been recorded