XVI INTRODUCTION. 



they can elevate at pleasure, and seriously wound 

 any antagonist. 



THE SECOND SERIES OF FISHES, OR 

 CHONDROPTERYGII. 



Whilst the members of the first class, as already ob- 

 served, present a skeleton essentially osseous, the 

 skeletons of the chondropterygii are cartilaginous 

 only. The fishes of this series, however, are of 

 great power and magnitude, and are divided into 

 such as breathe by means of free gills, and such 

 as have confined branchiae. 



The First Order of Chondropterygii,or the Seventh Order of 

 Fishes, generally embraces the Sturiones, or chon- 

 dropterygious tribes, with free gills. The sturgeon, 

 which is the most prominent of these, is well 

 known for his great size, the firmness of his flesh, 

 and the mailing of his skin. 



The Second Order of Chondropterygii^ the Eighth Order 

 of Fishes generally, is composed of such as have 

 fixed gills ; that is, of such as, instead of having 

 gills free at the external edge, which allows the water 

 to escape by one common opening, eject it by a 

 series of holes or perforations in the common inte- 

 gument. Of the genera which compose this order, 

 the Shark and Ray are the most prominent in- 

 stances. 



