Twenty different species of this family are known, and the number of different families of the Shark tribe is very great.
THE GREENLAND SHARK, (Selachus maximus,)
Is another very voracious species; and one extremely difficult to kill. It is the great enemy of the whale, and devours the bodies of those left by the fishers. Its teeth are very small, pointed, and numerous. The snout is short. It is sometimes known as the Basking Shark.
THE DOG-FISHES
Are so excessively voracious, that they are altogether fearless of mankind. They follow vessels with great eagerness, seizing with avidity everything eatable that is thrown overboard; and have sometimes been known to throw themselves on fishermen, and on persons bathing in the sea. As, however, they are much smaller and weaker than most of the other Sharks, they do not always attack their enemies by open force, but generally have recourse to stratagem. They, consequently, conceal themselves in the mud, and lie in ambush, like the ray or skate-fish, (also one of the cartilaginous fishes,) until they have an opportunity of successfully attacking their prey. On the coasts of Scarborough, where haddocks, cod, and Dog-fish are in great abundance, the fishermen universally believe that the Dog-fish make a line or semicircle to encompass a shoal of haddocks and cod, confining them within certain limits near the shore, and eating them as occasion requires: they are therefore considered very destructive to this fishery. The flesh of the Dog-fish is hard and disagreeable; its skin, when dried, is made into the well-known shagreen, and from the liver a considerable quantity of oil may be extracted. Shagreen is also made from the skin of other cartilaginous fishes.