Fishes . odon spatula andPsephiirus gladiiis) the snout is spread out forming a broadpaddle or spatula. This the animal uses to stir up the mudon the bottoms of rivers, the small organisms contained inmud constituting food. Similar paddle-like projections aredeveloped in certain deep-water Chimseras {Harriotita, Rhino-chvucrra), and in the deep-sea shark, Mitsukurina. The Sawfishes.—A certain genus of rays (Pristis, the saw-fish) and a genus of sharks {Pristiophorus, the saw-shark), pos-sess a similar spatula-shaped snout. But in these fishes thesnout is provided on either side with enamelled

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Fishes . odon spatula andPsephiirus gladiiis) the snout is spread out forming a broadpaddle or spatula. This the animal uses to stir up the mudon the bottoms of rivers, the small organisms contained inmud constituting food. Similar paddle-like projections aredeveloped in certain deep-water Chimseras {Harriotita, Rhino-chvucrra), and in the deep-sea shark, Mitsukurina. The Sawfishes.—A certain genus of rays (Pristis, the saw-fish) and a genus of sharks {Pristiophorus, the saw-shark), pos-sess a similar spatula-shaped snout. But in these fishes thesnout is provided on either side with enamelled teeth set insockets and standing at right angles with the snout. Theanimal swims through schools of sardines and anchovies, strikes I Adaptations of Fishes 73 right and left with this saw, destroying the small fishes, whothus become an easy prey. These fishes live in estuaries andriver mouths, Pristis in tropical America and Guinea, Pristi-opkorus in Japan and Australia. In the mythology of science, the. Fig. 55.—Saw-shark, Pristiophorus japonicus Giinther. Specimen from Nagasaki. sawfish attacks the whale, but in fact the two animals nevercome within miles of each other, and the sawfish is an object ofdanger only to the tender fishes, the small fry of the sea. Peculiarties of Jaws and Teeth.—The jaws of fishes are sub-ject to a great variety of modifications. In some the bones arejoined by distensible ligaments and the fish can swallow otherfishes larger than itself. In other cases the jaws are excessivelysmall and toothless, at the end of a long tube, so ineffective inappearance that it is a marvel that the fish can swallow any-thing at all. In the thread-eels (Nemichthys) the jaws are so recur^-edthat they cannot possibly meet, and in their great length seemworse than useless. In some species the knife-like canines of the lower jaw piercethrough the substance of the upper. In four different and wholly unrelated groups of fishes theteeth are grown fast together, forming