538 The True Sharks 



Is urns oxyrhynchus occurs in the Mediterranean, Isuropsis dekayi, 



in the Gulf of Mexico, and Isuropsis glauca, from Hawaii and 



Japan westward to the Red Sea. 



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 Linnaeus, it is the 

 animal which swallowed the prophet Jonah. 

 " Jonam Prophetum," he observes, "ut veteris 

 Herculem trinoctem, in huius ventriculo tri- 



FIG. 331. Tooth of , . i . ., , ,, 



hastalis dui spateo D82sisse, verosimile est. 



(Agassiz). Mio- j t j s beyond comparison the most vo- 



cene. Family Lam- ..,,,., . T 



nidce. (AfterNich- racious of fish-like animals. Near Sequel, 

 California, the writer obtained a speci- 

 men in 1880, with a young sea-lion (Zalophus) in its stomach. 

 It has been taken on the coasts of Europe, New England, Caro- 

 lina, 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 Lamnidcz. 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 

 Cor ax is also placed here by Woodward. 



