PRIMARY DIVISIONS OF THE MALACOPTERYGES. 227 



or salmons ; while the second, or sub-typical, seem to 

 be the Pleuronectidcs, or flat fish ; then follow the three 

 aberrant groups, represented by the Gadidcs, or cods, the 

 SiluridcBy or cat-fish, and the CobitidcB, or loaches. That all 

 these groups are united into one great circle, is evident : 

 for although, in tracing the series, we shall find an hiatus, 

 which nothing yet known can fill up, there is yet such 

 circumstantial evidence proving the series of those forms 

 which we already know to be natural, that we can only 

 look upon the inequality of the links as arising from 

 one or other of those causes elsewhere explained. We 

 here allude to the interval between the Salmonidce and 

 the Pleuronectidce, or flat fish. All ichthyologists agree 

 in considering these latter to be the most isolated group 

 among fishes, just as the Psittacidce, or parrots, are 

 among birds; and for the same cause, namely, that there 

 are no forms among them so aberrant as to mark beyond 

 doubt the character of the group by which they are pre- 

 ceded, and that, again, by which they are followed. In 

 deciding, therefore, the probable station which such an 

 apparently isolated group would hold, we must have re- 

 course to inductive reasoning. First, then, there can be no 

 doubt on the acknowledged fact, that the PUuronectidcB 

 belong to this order, not merely because all writers have 

 so placed them, but because they would interrupt the se- 

 ries of the other circles; and, further, because they have 

 some affinity to the GadidcB, near to which M. Cuvier, 

 following all his predecessors, has placed them ; both 

 having the anatomical character of the ventral fins being 

 attached to the pectorals, and the pelvis immediately 

 suspended to the bones of the shoulder. This affinity, 

 therefore, being established, we have only to follow the 

 thread of progression from Gadus to the next and to 

 the next family, until, having gone as far as we can, 

 and successively established our groups as we proceeded, 

 there is no other conclusion to be made than this,^ — that 

 where the line of affinity becomes lost, is precisely where 

 those forms which should lead us back again from our 

 starting post is wanting. Now, this is a precisely ana- 



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