32 CLASSiyiCATION OF FISHES. 



implies that it should have as fev,- aberrant or imper- 

 fectly organised types as possible; for otherwise it 

 would not, in one sense, be eminently t^^ical. This 

 reason, by the way, is eouallv valid as a creneral ex- 

 planation why nearly all aberrant groups in the higher 

 classes of the animal creation, are so very inferior in 

 point of numbers to such as are typical. * Having 

 now shown the analogy of the EcheneidcE to the Apode."--, 

 that of Centriscus to the cheloniform fishes is obvious 

 to every one. The CoryplierddcE, or dolphins, like the 

 Cartilagines, or sharks, are remarkable for their blunt 

 head, which is very much rounded, and projects over the 

 mouth : in one, indeed, the head is compressed, and in 

 the other depressed ; but still the analogous character is 

 beautifully preserved ; and the great head, so prevalent 

 in these groups, is only the modification of the fissi- 

 rostral type among birds, and of the CetcF among the 

 Mammalia. These fishes, also, have the largest and the 

 most powerful fins of any others in this group, just as 

 the fissirostral birds have invariably the largest wings, 

 both indicating peculiar swiftness either in swimming 

 or in flying. 



^V'e may now turn to another test ; and we shall find, 

 by comparing the contents of this tribe with that of 

 the entire circle of the spiniferous order, that m^any 

 other beautiful relations will be ehcited. 



Annhgifi.f of the Microleptes to the Acanthopterygfs. 



Families of the . Tribes of the 



MicroUptes. Analogies. Acanthopteryges. 



Scomberida. \ ^Ccdes particularly mial! ; body ) Microleptes. 



I lengthened. 3 



Zeid^. \ Eody oval ; short prickles in- 7 Macroleptes. 



t stead of dorsal spines. 3 



i fins without spinous rays. 3 



r^t^^^A^ f Bodv covered with hard sea-") ^ 



Centrtscida. ^ brbus scales or plates. ^ j Canthileptes. 



C Body excessively compressed ; ^ 

 Coryphtsnidte. < head very obtuse.: fins very C Gym netres, 

 C long or broad. ' j 



• A striking exception, however, to this rule is presented by the order 



