CLASS PISCES 453 



food of Polyodon consists largely of minute plants and ani- 

 mals, of which enormous numbers are devoured. The paddle- 



FIG. 381. The spoonbill sturgeon or paddle-fish, Polyodon spathula, 

 ventral and side view. (From Dean, after Goode.) 



fish is good to eat, but its roe, from which caviar is made, is more 

 valuable than its flesh. 



The family ACIPENSERID^E contains two genera of sturgeons, 

 Acipenser and Scaphirhynchus. They inhabit the seas, lakes, 

 and rivers of Europe, Asia, and America. Sturgeons possess a 

 cephalic prolongation or rostrum which bears on its ventral 

 surface a number of tactile filaments called barbels. The 

 scales form five longitudinal rows of bony scutes between which 

 are smaller ossifications. The mouth lacks teeth. The common 



FIG. 382. The common sturgeon, Acipenser sturio. (From Dean, 

 after Goode.) 



sturgeon, Acipenser sturio (Fig. 382), lives along the Atlantic 

 coast arid ascends the rivers of northern Europe and the United 

 States. Acipenser rubicundus is the sturgeon of the rivers and 

 lakes of the middle west. It feeds on the bottom, using its snout 



