They are, however, nowhere very common. The teeth of Dalatias major exist in Miocene rocks. In the genus Somniosus the species are of very much greater size, Somniosus microcephalus attaining the length of about twenty-five feet. This species, known as the sleeper-shark or Greenland shark, lives in all cold seas and is an especial enemy of the whale, from which it bites large masses of flesh with a ferocity hardly to be expected from its clumsy appearance. From its habit of feeding on fish-offal, it is known in New England as "gurry-shark." Its small quadrate teeth are very much like those of the dogfish, their tips so turned aside as to form a cutting edge. The species is stout in form and sluggish in movement. It is taken for its liver in the north Atlantic on both coasts in Puget Sound and Bering Sea, and I have seen it in the markets of Tokyo. In Alaska it abounds about the salmon canneries feeding on the refuse.
Family Echinorhinidæ.—The bramble-sharks, Echinorhinidæ, differ in the posterior insertion of the very small dorsal fins, and in the presence of scattered round tubercles, like the thorns of a bramble instead of shagreen. The single species, Echinorhinus spinosus reaches a large size. It is rather scarce on the coasts of Europe, and was once taken on Cape Cod. The teeth of an extinct species, Echinorhinus richardi, are found in the Pliocene.
Fig. 340.—Brain of Monkfish, Squatina squatina L. (After Duméril.)
Suborder Rhinæ.—The suborder Rhinæ includes those sharks having the vertebræ tectospondylous, that is, with two or more series of calcified lamellæ, as on the rays. They are transitional forms, as near the rays as the sharks, although having the gill-openings rather lateral than inferior, the great pectoral fins being separated by a notch from the head.
The principal family is that of the angel-fishes, or monkfishes (Squatinidæ). In this group the body is depressed and flat like that of a ray. The greatly enlarged pectorals form a sort of shoulder in front alongside of the gill-openings, which has suggested the bend of the angel's wing. The dorsals are small and far back, the tail is slender with small fins, all these being characters shared by the rays. But one genus is now extant, widely diffused in warm seas. The species if really distinct are all very close to the European Squatina squatina. This is a moderate-sized shark of sluggish habit feeding on crabs and shells, which it crushes with its small, pointed, nail-shaped teeth. Numerous fossil species of Squatina are found from the Triassic and Cretaceous, Squatina alifera being the best known.
Fig. 341.—Saw-shark, Pristiophorus japonicus Günther. Specimen from Nagasaki.
Family Pristiophoridæ, or Saw-sharks.—Another highly aberrant family is that of the sawsharks, Pristiophoridæ. These are small sharks, much like the Dalatiidæ in appearance, but with the snout produced into a long flat blade, on either side of which is a row of rather small sharp enameled teeth. These teeth are smaller and sharper than in the sawfish (Pristis), and the whole animal is much smaller than its analogue among the rays. This saw must be an effective weapon among the schools of herring and anchovies on which the sawsharks feed. The true teeth are small, sharp, and close-set. The few species of sawsharks are marine, inhabiting the shores of eastern Asia and Australia. Pristiophorus japonicus is found rather sparsely along the shores of Japan. The vertebræ in this group are also tectospondylous. Both the Squatina and Pristiophorus represent a perfect transition from the sharks and rays. We regard them as sharks only because the gill-openings are on the side, not crowded downward to the under side of the body-disk. As fossil, Pristiophorus is known only from a few detached vertebræ found in Germany.