Fox-shark, or THRESHER (Alopecias vulpes), the commonest of the larger sharks occasionally seen off British coasts. It is the only species of its genus, and is widely distributed in the Atlantic and Mediterranean, also occurring off California and New Zealand. It is much smaller than the basking shark (Selache maxima), but attains a length of over 12 feet, of which half goes to the enormously elongated upper lobe of the tail, to the length and splashing activity of which the fish owes its names. The pectoral limb and the first dorsal fin are large; the snout is conical; the mouth and gill-apertures are moderately wide; the teeth are triangular and not serrated; the skin is bluish above, flesh-coloured below. The fox-shark follows shoals of herrings, pilchards, and the like, threshing the water with its tail as it swims round its victims, which it destroys in great numbers. In spite of its size it is not dangerous to man; and though some of the stories of its attacks on large whales are exaggerated, it has been seen to punish them severely. See SHARK.