. Fishes. Fishes. The True Sharks 193 length. In the Upper Cretaceous is a very similar genus, Scapanorhynchus {lewisi, etc.), which Professor Woodward thinks may be even generically identical with Mitsukurina, though there is considerable difference in the form of the still longer rostral plate, and the species of Scapanorhynchus differ among themselves in this regard. Mitsukurina, with Heterodontus, Heptranchias, and Chlamy- doselache, is a very remarkable survival of a very ancient Fig. 134.—Scapanorhynchus levifti Davis. Family Milsukurinidce. Under side of snout. (After Woodward.)
. Fishes. Fishes. The True Sharks 193 length. In the Upper Cretaceous is a very similar genus, Scapanorhynchus {lewisi, etc.), which Professor Woodward thinks may be even generically identical with Mitsukurina, though there is considerable difference in the form of the still longer rostral plate, and the species of Scapanorhynchus differ among themselves in this regard. Mitsukurina, with Heterodontus, Heptranchias, and Chlamy- doselache, is a very remarkable survival of a very ancient Fig. 134.—Scapanorhynchus levifti Davis. Family Milsukurinidce. Under side of snout. (After Woodward.) It is an interesting fact that the center of abundance of all these relics of ancient life is in the Black Current, or Gulf Stream, of Japan. Family Alopiidae, or Thresher Sharks.—The related family of AlopiidcE contains probably but one recent species, the great fox-shark, or thresher, found in all warm seas. In this species, Alopias vulpes, the tail is as long as the rest of the body and bent upward from the base. The snout is very short, and the teeth are small and close-set. The species reaches a length of about twenty-five feet. It is not especially ferocious, and the current stories of its attacks on whales probably arise from a mistake of the observers, who have taken the great killer, Orca, for a shark. The killer is a mammal, allied to the por- poise. It attacks the whale with great ferocity, chnging to its flesh by its strong teeth. The whale rolls over and over, throwing the killer into the air, and sailors report it as a thresher. As a matter of fact the thresher very rarely if ever attacks any animal except small fish. It is said to use its tail in round- ing up and destroying schools of herring and sardines. Fossil teeth of thresher-sharks of some species are found from the Miocene. Family Pseudotriakidae.—The Pseudotriakidw consist of two species. One of these is Pseudotriakis microdon, a large shark. Please note that these images are extracted from scanned
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