278 PISCES. 



their reduction to mere vestiges concealed under the skin^ 

 while their functions are fulfilled by bones analogous to the 

 palatines, and even sometimes by the vomer. The gelatinous 

 substance, which in other fishes fills the intervals of the ver- 

 tebrse, and only communicates with them by a small hole, forms 

 a long cord in several of the Choiidropterygii, which traverses 

 the bodies of almost all the vertebrae, without scarcely vary- 

 ing in diameter. 



This series is divided into two orders the Chondropterygii 

 whose branchiae are free, like those of ordinary fishes, and 

 those in which they are fixed, that is to say, attached to the 

 skin by their external edge in such a manner that the water 

 can only escape from their intervals through holes on the 

 surface. 



ORDER I. 



STURIONES, OR CHONDROPTERYGII BRANCHIIS 



LIBERIS. 



Or Chondropterygii, with free branchiae, which are still 

 closely allied to the ordinary fishes in their gills, which have but 

 a single wide opening, and are furnished with an operculum, 

 but without rays in the membrane. This order comprises but 

 two genera. 



AciPENSER, Lin.(l) 



The general form of the Sturgeon is similar to that of the Shark, 

 but the body is more or less covered with bony plates in longitudi- 

 nal rows; the exterior portion of the head is also well mailed; the 

 mouth, placed under the snout, is small and edentated,' the palatine, 

 soldered to the maxillaries, converts ihem into the upper jaw, and 

 vestiges of the intermaxillaries are found in the thickness of the lips. 

 This mouth, placed on a pedicle that has three articulations, is more 



(1) Acifenser is the ancient name; Sturio, whence Sturgeon, is modern, and is 

 probably the German name fStoer latinized. 



