102 CLASSIFICATION OF FISHES. 



sessing ventral fins, and by the following additional 

 peculiarities : — the body is thick, very short, heavy, and 

 often, as it were, deformed ; the ventral fins are placed 

 upon a peduncle, so that they may be used, in some de- 

 gree, as feet, enabling the animal to crawl on the 

 ground ; the eyes are small, and placed nearly vertically ; 

 the mouth opens in the same direction, and has the 

 under jaw longest : in the most typical family, the 

 body is soft; but in the sub-typical, it is either covered 

 with osseous plates soldered together, or with acute 

 prickles: the ribs are almost always wanting; and 

 they are the only fishes which have the anatomical cha- 

 racter of the maxillary bone and the palatine, arch in- 

 serted in the cranium. Adopting Cuvier's name for 

 these fish, rather than that of Linnaeus, which was 

 founded in error, we term this order the Plecto- 

 gxathes, or cheloniform fishes. 



(90.) The fifth and last primary group consists 

 of those truly cartilaginous families which have the fins 

 and mouth of ordinary fishes, but who breathe by one 

 or more spiracles : the mouth is placed beneath the 

 snout, which is very broad and projecting ; the major 

 part are viviparous ; and the body is smooth, or, at 

 least, destitute of true scales. The sharks and rays are 

 the best known, and are the most typical of these fish, 

 which, as indicating their typical character, we propose 

 to call the Cartilagixes. 



(91.) That there is every reason to believe these 

 primary divisions of the class are founded in nature, 

 will be apparent from their accordance to the divisions 

 of the same rank that have been generally adopted by 

 the most eminent zoologists. Without attempting, in 

 our present rapid course, to show in what manner they 

 blend into each other and form one great circle, we 

 shall at once proceed to compare them in the order in 

 which they have been noticed, with other groups better 

 authenticated, or rather, we should say, more familiarly 

 known to naturalists. If we are successful in this 

 effort to establish a uniformity of analogical relations 



