THE CENTRONOTIN^. 39 



mucli confirm the general belief, that the pilot-fish is 

 sometimes a most useful friend to the shark. 



(38.) Naucrates brings us immediately into the circle 

 of the genus Centronotus, distinguished at once from that 

 of Seriola, by having but a single dorsal fin ; the ante- 

 rior prickles being very shorty and without any connect- 

 ing membrane : even in this generic group we find the 

 minor divisions preserve their analogy to the great types 

 of this order ; thus in Scorpis, the fins are covered (as 

 in the Chcetodons) with minute scales, but those of 

 Centronotus proper, are quite bare. Leaving these, our 

 next genus is Elacate, where the body is still longer and 

 narrower than in any of the preceding; it is, in fact, 

 eel-shaped, and shows its affinity to Sphyrcena,mtoyf\iich. 

 it passes, by having the lower jaw longest, the mouth wide, 

 and the lateral line sinuated : under this we have assem- 

 bled several remarkable sub-genera, possessing more or 

 less the same characters, and representing the contents 

 of the groups we have already gone through : the little 

 PorthmeuSy for instance, has the precise shaped. head of 

 Elacate, and with the commencement of a second dorsal ; 

 while, by its close resemblance, in other respects, to our 

 Zonicthys, we are at once brought into the fifth and last 

 division, namely, Trachinus. This group includes the 

 horse mackarel, and all those of the same general form 

 and structure, which, besides possessing two dorsal fins, 

 have the lateral line armed with a series of large scales 

 or plates, each terminated in a spine, so that the lateral 

 line becomes mailed, and is indicated by a row of 

 prickles pointing backwards : this is precisely analogous 

 to what we see in the sticklebacks and the gurnards; 

 and hence we conclude that the whole of these groups are 

 analogous to each other. Trachinus is very numerous 

 in species, particularly in the Indian seas; and the flesh 

 of aU we have met with is very fine. Of the five sub- 

 genera, that of Caranx is chiefly found near the tropics ; 

 while several species of true Trachinus (regarded as but 

 one by Cuvier and Valenciennes) occur in the Medi- 

 terranean and other European seas. "We thus close the 



D 4 



