FISHES. 381 



24. ACCIPENSER. Snout obtusely conical. A. sturio. 



25. SPATULARIA Snout laterally enlarged. S. vulga- 

 rw, 



ORDER IL 



OSSEOUS FISHES. 



THE bones of the fishes of this order possess a greater 

 degree of hardness than the cartilaginous kinds, and the 

 earthy matter is obviously arranged in a fibrous form. The 

 articulations are more distinct. The bones of the head are 

 divided by sutures. The gills are always free. 



1st Subdivision. 



Jaws imperfect. 



This includes the Plectognathes of CUVIER. The bones 

 are comparatively soft. The intermaxillary bones form 

 the jaw, to which the maxillary bone is firmly fixed. The 

 palatine bones are fixed to the cranium by a suture. These 

 conditions restrain all relative motion among the bones. 

 The ribs are imperfect. There are no ventral fins. Intes- 

 tinal canal large, without cceca. 



1st Tribe. 



Jaws exposed and covered with ivory. 



The jaws are here formed to act like the beak of a bird. 



There are no true teeth, but the jaws being produced 

 and hooked, supply their place. Gill-flap, with six rays. 



A. Body capable of being inflated at pleasure. The in- 

 flation is produced by air sent from the gills, into a sac 

 formed of a duplicature of the peritoneum, and from thence 

 into the abdomen. The inflation aids the animal in rising 

 in the water, and as the abdomen is covered with spines, it 

 brings these organs of defence into a more favourable posi- 

 tion for resistance. The air-bag has two lobes. The gills 



