SHARKS 5 



The teeth are different in the two jaws, but are mostly flattened 

 and more or less comb-like in character (Fig. 59) . The spiracles 

 are small, and the external gill-clefts, 6 or 7 in number on each 

 side, are all placed in front of the pectoral fins. There is only 

 1 dorsal and 1 anal fin, and both are without spines. There is 

 no pit at the root of the caudal fin. 



The Comb-toothed Sharks are found in all warm seas, but 

 as a rule are not numerous. All are viviparous. Fossil 

 remains, mostly teeth, date back to the Cretaceous period. 



SIX-GILLED SHARK OR GRISET. 



(Genus Hexanchus.) Fig. 7. 



There are 6 external gill-clefts on each side. The coloration 

 is uniformly dark brownish-grey or black above, shading to 

 paler below ; there is usually a pale streak along the middle 

 of each side. Young individuals are brown. 



Grows to a length of 26 feet or more. 



The single known species (H. griseus) is found in the Mediter- 

 ranean, Atlantic and Pacific. The so-called Shovel-nosed 

 Shark (H. corinus) from the coast of California is probably 

 only a variety. 



Little is known of the habits of this shark, but it is believed 

 to be fierce and voracious, and to feed almost entirely upon 

 fishes. It occasionally strays close to the British coasts, 

 especially in the summer months, and there is a record of 

 one, 26 feet 5 inches long, caught at Polperro, Cornwall, in 

 February, 1846. It is of no use as food, and those who have 

 sampled the flesh report a strong purgative effect. 



SEVEN-GILLED SHARK OR PERLON. 



(Genus Heptranchias.) Fig. 8. 



There are 7 external gill-clefts on each side. The coloration 

 is brown or grey above, shading to paler below ; the back, 

 especially in the young, is sometimes provided with small, 

 scattered, dark spots. 



Grows to a length of more than 10 feet. 



The Perlon {H. perlo) is found in the Mediterranean, in the 



