ORDER GANOIDEI; ACIPKXSERID.E. 41 



opercuium usually bears a supplementary branchia, and below 

 this there is frequently a false gill, which only receives arterial- 

 ized blood. The top of the head is often furnished with a pair 

 of spiracles, which also occur in some Sharks. 



595. The recent Fishes of this order form five families. Two 

 of these belong to the cartilaginous section of the order, the 

 Chondrostei of Professor Miiller, these are the ACIPENSERID^E, 

 or Sturgeons ; and the SPATULARID^, or Leaf -nosed Sturgeons. 

 The others belong to the Holostei of Miiller, possessing a true 

 bony skeleton, these are the LEPIDOSTEID^E, or Bony -pikes ; 

 the POLYPTERID^E, or Fin-pikes ; and the AMIID^E, or Bald- 

 pikes. 



596. In the ACIPENSERID^E, or Sturgeons, the body is more 



FIO. 372.- BELUGA. 



or less covered with bony plates, arranged in longitudinal rows ; 

 and the head is armed with the same. The mouth is situated 

 beneath the elongated muzzle, and is small, toothless, and pro- 

 trusible ; in front of it a few longish barbs hang down from the 

 snout. The air-bladder is very large, and communicates by a 

 wide opening with the gullet ; and in this, and other points of 

 their internal conformation, the Sturgeons show a considerable 

 approach to the Lizards, whence they are ranked among the 

 Sauroid fishes. The tail is very unsymmetrical. Sturgeons, 

 like Salmon, ascend large rivers for the purpose of spawning ; 

 and they are the subject of valuable fisheries. They are more 

 abundant in the Continental rivers than in those of Britain ; 

 id are particularly numerous in those which fall into the Black 

 and Caspian seas. The common Sturgeon attains the length of 

 six feet; but the great Sturgeon, or Beluga, has been found 

 twelve or even fifteen feet in length, and weighing from 1200 to 

 3000 Ibs. The flesh of the former is very palatable and whole- 

 some, resembling veal in its character ; that of the latter, how- 



