Saw Fish, a cartilaginous fish of the genus pristis (Lath.), the type of a family intermediate in position between the sharks and rays, though generally ranked with the latter. It has the elongated and rounded form of a shark, with the mouth and gill openings on the ventral surface as in rays. Its distinguishing character is the long, flattened, narrow, and straight snout, set on the sides with teeth or strong bony spines, forming a double-edged saw-like weapon, whence the common name. The true jaw teeth are very small, and pavement-like as in the rays; the body is flattened in front of the pectorals, the posterior portion and the tail as in sharks; the skin is covered with small rough scales; the pectorals are distant from the head, and not extending to the ventrals; the tail has two dorsals, and a caudal fin prolonged as in the sharks. About half a dozen species are described, found in arctic, tropical, and antarctic seas, and one all along the coast from New England to Florida;, they are rapid swimmers. The beak attains a length of from one fourth to one third the total length of the body; it is covered with a rough skin, and is narrower toward the end, which is rounded; this beak has been found driven deeply into the timbers of ships.
They seem to have a natural antipathy to the larger cetaceans, and many voyagers have been witnesses to. their victories over them. The jaw teeth are adapted for crushing crustaceans and similar animals upon which they feed, and not for tearing flesh. According to Owen, the beak is composed of the cartilages attached to the frontal, nasal, and vomerine bones blended into a horizontal flattened plate, which is more completely ossified than any other part of the skeleton; a series of deep sockets on each of the lateral margins contain the teeth, which are solid, the base being slightly concave and porous, and the spaces between them hollow and filled with a gelatinous medulla, rendering it light without diminishing its strength; vessels and nerves supply the teeth, which grow by constant addition of ossified pulp material at the base. Though the projections of the beak are implanted like teeth, they have no relation to the intestinal canal, and are turned outward like spines of the external or der-matoskeleton; they form a very interesting transition between teeth and cutaneous spines.
These teeth wound by repeated blows, and not by cutting like a saw; the Polynesians use this beak as a sword. - The common saw fish is the P. antiquorum (Lath.), which attains a length of 12 to 15 ft., of which the beak is about one third, with 20 to 30 teeth on each side; it is blackish gray above, and lighter below; the eyes are large, the nostrils in front of the mouth protected by a membranous fold, and two oval foramina behind the eyes. Klein says that in the embryo the sides of the snout are as smooth as the gums of a new-born infant; but according to Latham they grow very rapidly after birth, and are not shed and replaced like the teeth of mammalian jaws.
Common Saw Fish (Pristis antiquorum).