278 PISCES. 



tlieir 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- 

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

 a long cord in several of the (>hondro[>tcrygii, which traverses 

 the bodies of almost all the vertebra', without scarcely vary- 

 ing in diameter. 



This series is divided into two orders — the Chondropterygii 

 whose branchia*. 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. 



HTURIONES, OR CHONDROPTERYGII BRANCIIIIS 

 LIliKRIS. 



Or Chondropterygii, with free branchiae, which are still 

 closely allied to the oidinary fishes in tlieir 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. 



AciPENSEu, Lin.(l) 



The general form of the Sturtjeon is similar lo that of the Shark, 

 bul 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 tlie snout, is small and edentated; the palatine, 

 soldered to the maxillaries, converts iheni into tlie upper jaw, and 

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

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



(1) Jldptnucr is llie iinclciit name; Slurio, whence Sturgeon, is iiiodcrn, and is 

 proljtiljly tlic (jcrmaii name iSlocr latinized. 



