The True Sharks 195 
Isurus oxyrhynchus occurs in the Mediterranean, Isuropsis dekayt, 
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 Linnzeus, it is the 
animal which swallowed the prophet Jonah. 
““Jonam Prophetum,’’ he observes, “ut veteris 
Herculem trinoctem, in hujus ventriculo tri- 
Fie. 137 —Tooth of : : een ” 
Isurus  hastalis GUI spateo beesisse, verosimile est. 
(Agassiz). Mio- It is beyond comparison the most vo- 
cene. Family Lam- : : : “ 
nide. (AfterNich- racious of fish-like animals. Near Soquel, 
gets) 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. 138), 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 Lamnide. 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. 
