542 



The True Sharks 



in warm seas and known as tiger-sharks {Galeocerdo macidatus 

 in the Atlantic, Galeocerdo tigrinus in the Pacific). 



The species of Carcharias {CarcharJiinus of Blainville) lack 

 the spiracles. These species are very numerous, voracious, 

 armed with sharp teeth, broad or narrow, and finely serrated 

 on both edges. Some of these sharks reach a length of thirty feet. 

 They are very destructive to other fishes, and often to fisher}' 

 apparatus as well. They are sometimes sought as food, more 

 often for the oil in their livers, but, as a rule, they arc rarely 

 caught except as a measure for getting rid of them. Of the 

 many species the best known is the broad-headed Carcharias 

 lamia, or cub-shark, of the Atlantic. This the writer has taken 

 with a great hook and chain from the wharves at Key West. 

 These great sharks swim about harbors in the tropics, acting as 



Fig. 335. — (-'ub-shark, Carcharias Imnia Rafinesque. Florida. 



scavengers and occasionally seizing arm or leg of those who 

 venture within their reach. One species {Carcharias iiicara- 

 gnciisis) is found in Lake Nicaragua, the only fresh-water shark 

 known, although some run up the brackish mouth of the Ganges 

 and into Lake Pontchartrain. Carcharias japonicus abounds in 

 Japan . 



A closely related genus is Prionace, its species Prionace 

 glauca, the great blue shark, being slender and swift, with the 

 dorsal farther back than in Carcharias. Of the remaining 

 genera the most important is Scoliodon, small sharks with 

 obhque teeth which have no serrature. One of these, Scoliodon 

 ierrcc-iwvce, is the common sharp-nosed shark of our Carolina 

 coast. Fossil teeth representing nearly ah of these genera 

 are common in Tertiary rocks. 



Probably allied to the Carchariidce is the genus Corax, 

 containing large extinct sharks of the Cretaceous wath broad- 



