CAUDAL FIN. 31 



swimming fish are all distinguished by a tail more or 

 less forked ; and that the most sluggish are invariably 

 characterised by a rounded tail. Now this is precisely 

 what we find in ornithology, where no instance is upon 

 record of a rounded tail and wings being given to swift 

 flying birds, or the reverse. Were we asked to name, 

 from our own experience, that family of fish whose 

 swimming was most rapid, we should hesitate between 

 the flying fish and their enemies, the different species 

 of tunnies, by which they are so frequently pursued : 

 the latter, indeed, would seem to have the superiority, 

 since they frequently overtake the other, upon which, 

 they are known to feed ; but this superiority lies more, 

 we apprehend, in their greater size and muscular 

 strength than in the absolute power of swimming : it 

 is clear, in fact, that if the strength of the flying fish 

 did not fail after a long chase, the bonatos or tunnies 

 could not overtake them, any more than the dog could 

 outstrip the hare. In both instances the superiority of 

 speed lies with the pursued, while that of muscular 

 strength is with the pursuer ; thence the latter qualifi- 

 cation, in the end, triumphs over the former. Now the 

 whole of the Scomberidce, or tunny family, have the 

 tail more deeply forked than any other fishes, perhaps, 

 in the entire class ; for not only are the two lobes deeply 

 cleft, but in most instances they are actually divided ; 

 and they are further provided with two additional finlets 

 on each side, by which the rapidity of motion is 

 doubtless accelerated : this is further increased, in many 

 groups of this family, by a prominent fleshy keel 

 which projects on each side, near the base of the caudal 

 fin, and parallel to the lateral line : these ridges are ob- 

 viously intended to cut the water on each side, and they 

 are only found among those families we have arranged in 

 the tribe of Macroleptes. Forked tails are only found 

 among the two great divisions of osseous fishes, and 

 a few of their representatives ; for those of the sharks, 

 when they approach this form, are more properly 

 Jobed or emars-inate in the middle, the lobes themselves 



