120 CLASSIFICATION OF FISHES. 



places the birds after the reptiles^ the quadrupeds after 

 the birds^ and the fishes after the quadrupeds_, without 

 ha\dng the least suspicion thatj ahhough this series was 

 natural^ it possessed another property, by which the 

 amphibians, the reptiles, and the fish, formed a primary 

 circle of their own ; and thus reduced the three aberrant 

 divisions into one. The cartilaginous fishes, in short, unite 

 the aberrant divisions of the vertebrated circle into one ; 

 while, at the same time, they open a passage to the 

 quadrupeds by means of the whales, the dolphins, and 

 the porpoises. If the student wishes to comprehend 

 this double affinity, let him compare the figures of the 

 Ichthyosaurus with that of a shark, and he will be 

 immediately convinced that no reptile so much resembles 

 a fish as does the Ichthyosaurus: again, if he looks to 

 the porpoise, its resemblance to the cartilaginous fish is 

 so peculiarly striking, that he will be not at all sur- 

 prised at the older naturalists placing them in the same 

 class. 



(107-) The views we have taken of the cartilaginous 

 order in other respects are so different from those of M. 

 Cuvier, that we deem it necessary, in this place, to explain 

 our reasons. Although the arrangement of this order in 

 the Regne Animal is confessedly artificial, it is liable to 

 much fewer objections than usually attend such methods, 

 because the two typical divisions (the sharks and the 

 rays) are so pecuharly marked, that upon this point 

 there never had been the least difference of opinion. 

 The only objections, therefore, that may be made to his 

 remaining series, regard the aberrant groups". It is 

 quite evident, that if all fishes whose bones are car- 

 tilaginous are to be placed in this order, the genera 

 LeptocephaJus, Lophius, Cyclopterus, and several others, 

 have as great a claim to be associated with the sbarks 

 and rays as Petromyson ; while, if we extend the 

 order to such as have the branchia so hid, that they only 

 present an external slit, the order must be enlarged 

 so as to include the eels and several cognate genera. 

 Both these principles appear equally objectionable ; the 



