280 CLASSIFICATION OF FISHES. 



in accordance with all we have said on the nature and 

 properties of natural groups^ — the close affinities between 

 each of the types in the first column^ or the beautiful 

 analogies which they find in the primary divisions of 

 the ClupeincB. We here deal^ in the first instance^ with 

 factSj and facts only ; — the inferences are an after 

 consideration ; but they are just as strong, to any mind 

 which understands the nature of inductive reasoning, as 

 the facts themselves ; and to those who do not compre- 

 hend the Baconian philosophy^ all argument is useless. 

 Addressing ourselves^ therefore, to the former^ how 

 singularly does Thryssus and Osteoglossum represent 

 each other by their enormously wide mouth — cleft in 

 an oblique direction, and armed with single detached 

 teeth : this structure, with the slight projection of the 

 muzzle, immediately reminds us of the sharks and the 

 pikes, which these fishes, as being representatives of the 

 cartilaginous type, so singularly represent, as well as 

 Xiphostoma, and numerous others. The completely 

 vertical mouth of Fristogaster, with the entire absence 

 of the ventrals, reminds us immediately of Chiro- 

 nectes by the first character, and of Balistes by the 

 second ; while, if we look for a repetition of these forms 

 under a different modification among the salmons, we 

 are at once presented with Sternoptyx, more especially 

 resembling the American Pristogaster Martii of Spix. 

 The disappearance of the ventrals, and the great deve- 

 lopment of the anal fins, no less than the superior length 

 of the tail (or, what is the same thing, the proximity 

 of the vent to the pectorals), is a very general character 

 among the apodal fishes ; and one or both of these cha- 

 racters are also seen in Platygaster and Chirocentrus ; 

 although, as the latter, by the backward position of its 

 dorsal, passes into the pikes, it assimilates even more to 

 that group than to Platygaster. "We had almost forgotten 

 to notice the wonderful resemblance between Chatoessus 

 and Megalops, — a resemblance so strong to a superficial 

 eye, that none but an ichthyologist would detect their 

 absolute difference : both have the elongated form of the 



