18 CLASSIFICATION OF FISHES. 



haunts of these marine creatures : the most we can do, 

 is to found our conjectures, on such matters, upon ana- 

 logical reasoning. 



(21.) The pectoral fins, as being the wings of fishes, 

 are consequently found in the highest state of develop- 

 ment in such families as represent the fissirostral and 

 natatorial birds, whose powers of flight are so superior to 

 others. Hence we find that in the two chief families 

 of the cartilaginous order, namely, the sharks and rays, 

 these fins are universally very large, and in the latter they 

 are so much developed as to occupy more than one half 

 the surface of the body ; they appear, in fact, to be sur- 

 rounded and enveloped in their enormous pectorals, 

 which, being generally angulated or pointed, must give 

 to these rapacious monsters a swiftness of swimming 

 analogous to that possessed by their representatives, the 

 swallows, in flying. The pectorals of the sharks, 

 although not proportionably large, still exceed all the 

 other fins in size ; and thus render them such rapid 

 swimmers. The actual volatile powers of the flying- 

 fish is, likewise, entirely owing to the enormous size of 

 their pectorals ; but there is nothing peculiar in their 

 shape or construction, since they merely have the form 

 and structure of an ordinary pointed fin, only excessively 

 enlarged. Now, as we find these fins are very complete 

 in fishes which are constantly moving about in their 

 watery element, as birds do in the air, so, among such 

 as are more stationary, and swim but little, the pectorals 

 are proportionably small : this is particularly observable 

 in the family of the Pleuronectidce, or flat fish, whose 

 whole structure is adapted for laying flat upon the 

 bottom of the sea, and there waiting for their prey in 

 ambuscade. These fishes, in proportion to their size, 

 have the smallest pectorals in the whole class ; while 

 the flying fish, which habitually live only in the wide 

 ocean, and are perpetually traversing it, have the 

 largest. The Lophidce, or fish-frogs, again, may almost 

 be said to have no real pectoral fins, inasmuch as these 

 members are so formed as to perform the office of feet, 



