Ll6 CLASSIFICATION' OF FISHES. 



(which includes the crocodiles and most of the extinct 

 fossil genera) is very striking : both are the most gigan- 

 tic and ferocious inhabitants of the water ; and, like all 

 types pre-eminently aquatic, they have the head large, 

 the muzzle long and generally broad, the mouth large, 

 and armed with formidable teeth. The close resemblance, 

 again, between the tortoises and the mailed Plectogna- 

 thes require no additional evidence in support of their 

 perfect and beautiful analogy. Lastly, we have apodal 

 fishes, standing opposite to that most singular group of 

 reptiles represented by the chameleon. We shall not 

 here anticipate the reasons subsequently given for 

 placing these scansorial lizards as the representatives of 

 a distinct order ; but we may here call the attention of 

 the naturalist to the following resemblances existing 

 between these two groups. The locomotive mem- 

 bers of the chameleon assume, indeed, the form of feet, 

 and not of fins ; but then they are the least organised 

 feet of all the lizards, and are formed completely on the 

 scansorial model; the toes being in pairs, of which two 

 are placed forward and two backward : the tail, again, 

 as if to make up for this deficiency, is highly developed, 

 not so much in its length, as in the faculty it possesses 

 of being prehensile, so that it can be used, like that of 

 scansorial birds, as a hinder foot or support. Now, the 

 structure of the apodal fishes is singularly analogous to 

 ail this : the fins which represent the feet are entirely 

 wanting; while, at the same time, they have invariably 

 the longest tails. The apodal order passes into that of 

 the Acanthopteryges ; and they are as closely united as 

 the chameleons are to the Lacertes, or lizards. 



(102.) To pursue these details further appears un- 

 necessary. If we have been successful in determining 

 the primary types of the class now under consideration; 

 and if they truly represent, as here stated, the corre- 

 sponding types in the other vertebrated animals ; it fol- 

 lows that, through these latter, they represent all others 

 contained in our preceding volumes. These compari- 

 sons will amply repay the labour of those naturalists 



