Man-eating Sharks.—Equally swift and vastly stronger than these mackerel-sharks is the man-eater, or great white shark, Carcharodon carcharias. This shark, found occasionally in all warm seas, reaches a length of over thirty feet and has been known to devour men. According to Linnæus, it is the animal which swallowed the prophet Jonah. "Jonam Prophetum," he observes, "ut veteris Herculem trinoctem, in hujus ventriculo tridui spateo bæsisse, verosimile est."
Fig. 331.—Tooth of Isurus hastalis (Agassiz). Miocene. Family Lamnidæ. (After Nicholson.)
It is beyond comparison the most voracious of fish-like animals. Near Soquel, California, the writer obtained a specimen in 1880, with a young sea-lion (Zalophus) in its stomach. It has been taken on the coasts of Europe, New England, Carolina, California, Hawaii, and Japan, its distribution evidently girdling the globe. The genus Carcharodon is known at once by its broad, evenly triangular, knife-like teeth, with finely serrated edges, and without notch or cusp of any kind. But one species is now living. Fossil teeth are found from the Eocene. One of these, Carcharodon megalodon (Fig. 332), from fish-guano deposits in South Carolina and elsewhere, has teeth nearly six inches long. The animal could not have been less than ninety feet in length. These huge sharks can be but recently extinct, as their teeth have been dredged from the sea-bottom by the Challenger in the mid-Pacific.
Fossil teeth of Lamna and Isurus as well as of Carcharodon are found in great abundance in Cretaceous and Tertiary rocks. Among the earlier species are forms which connect these genera very closely.
The fossil genus Otodus must belong to the Lamnidæ. Its massive teeth with entire edges and blunt cusps at base are common in Cretaceous and Tertiary deposits. The teeth are formed much as in Lamna, but are blunter, heavier, and much less effective as instruments of destruction. The extinct genus Corax is also placed here by Woodward.
Fig. 332.—Carcharodon megalodon Charlesworth. Miocene. Family Lamnidæ. (After Zittel.)
Family Cetorhinidæ, or Basking Sharks.—The largest of all living sharks is the great basking shark (Cetorhinus maximus), constituting the family of Cetorhinidæ. This is the largest of all fishes, reaching a length of thirty-six feet and an enormous weight. It is a dull and sluggish animal of the northern seas, almost as inert as a sawlog, often floating slowly southward in pairs in the spring and caught occasionally by whalers for its liver. When caught, its huge flabby head spreads out wide on the ground, its weight in connection with the great size of the mouth-cavity rendering it shapeless. Although so clumsy and without spirit, it is said that a blow with its tail will crush an ordinary whaleboat. The basking shark is known on all northern coasts, but has most frequently been taken in the North Sea, and about Monterey Bay in California. From this locality specimens have been sent to the chief museums of Europe. In its external characters the basking shark has much in common with the man-eater. Its body is, however, relatively clumsy forward; its fins are lower, and its gill-openings are much broader, almost meeting under the throat. The great difference lies in the teeth, which in Cetorhinus are very small and weak, about 200 in each row. The basking shark, also called elephant-shark and bone-shark, does not pursue its prey, but feeds on small creatures to be taken without effort. Fossil teeth of Cetorhinus have been found from the Cretaceous, as also fossil gill-rakers, structures which in this shark are so long as to suggest whalebone.