CARTILAGINOUS FISHES. 



351 



imbedded in the skin in longitudinal rows. Their mouth is adapted 

 for suction, and unprovided with teeth. These fishes are generally 

 large, and endowed with considerable muscular strength. They 

 easily stem the most rapid cm-rent, and can strike violent blows with 

 their tail ,* but their habits are ordinarily peaceful, and they are 



Fig. 2S3. — the stukgeox (Acijienser Sturio). 



formidable only to small unarmed prey. They feed on herrings, 

 mackerel, and sometimes salmon, and also root in the mud for worms 

 and moUusks. In the spring they ascend certain rivers from the 

 sea, often in numerous shoals, to deposit their eggs. Their fecun- 

 dity is very great. We are assured that 1,. 500,000 eggs have been 

 found in a single female that weighed 270 lbs., and in another 

 weighing 2,800 lbs., the spawn alone weighed 800 lbs. 



The young ones seek the sea very early and re- 

 main there till full grown. The flesh is wholesome ; 

 and from their eggs a kind of food is prepared, much 

 esteemed in the north of Europe, called Caviar. It 

 is chiefly from the swimming bladder of these fishes 

 that isinglass is manufactured. 



The Pohjodon, or Spatidaria, a fish allied to 

 the Sturgeon, is found in the Mississippi; it is 

 remarkable for an enormous prolongation of the 

 muzzle, to wliich its wide borders give the figure of 

 a leaf. The mouth is well cleft, and furnished with 

 several small teeth. 



