Sharks. 



FIG. 12. 



The heart in sharks has a long arterial cone. The 

 intestine, though short, is very capacious, and has the 

 extent of its inner surface in- 

 creased enormously by means 

 of a long spiral fold of its 

 lining mucous membrane, 

 which stretches throughout 

 almost its whole extent. Like 

 the lampreys, sharks are de- 

 void of a swimming-bladder. 



Some sharks are vivipa- 

 rous (that is, produce their 

 young alive) ; in others the 

 young are extruded within 

 curious horny tendril-bearing 

 rases, which are often picked 

 up along the sea-shore, and 

 are commonly called ' mer- 

 maids' purses.' 



The commonest examples 

 of this order are the dog-fishes, 

 sharks, and rays. One of the 

 largest forms is the great bask- 

 ing shark of the North At- 

 lantic ; this fish is not at all 

 uncommon on the west coast 

 of Ireland, where it is called 

 the sun-fish, and is often cap- 

 tured for its oil. It also oc- 

 curs, though but rarely, on the 

 American coast. It often ex- 

 ceeds thirty feet in length, and a specimen of this 

 size will yield ninety gallons of oil from its liver. The 



Beak of saw-fish seen from Le- 

 low, showing its mout 

 nostrils, and lateral teeth. 



