16 CLASSIFICATION OF FISHES. 



thick, but is generally barbed on one or both sides, so 

 that it becomes a formidable weapon of defence. The 

 great importance of the pectoral fin to the rapid motion 

 of fishes is still further manifested by the fact that, in 

 all such groups as are peculiarly rapid, the pectoral 

 fin is pointed, or rather triangular. The flying fish, the 

 tunny family, the rays, are familiar examples of this 

 form in its highest state of development; while we 

 find the same, in a less degree, among the Spari, the 

 herrings (Clupeidce), the typical cod-fish, Gadiadce, 

 and many others. These, in fact, are nearly all pelagic 

 fishes, performing, like fissirostral birds, either annual 

 migrations, or living almost entirely in the open sea 

 except at the breeding season. In such families, on the 

 contrary, as live in rivers and lakes, or only in shallow 

 rocky shores, the pectoral fins are always round. The 

 whole of the apodal or anguilliform order, in which are 

 the eels, the lampreys, and the suckers, together with 

 the blennies, gobies, the rocklings (Motella), and nu- 

 merous other families, are of this description. Even the 

 Triglidce, or gurnards, and their allies, although their 

 pectorals are of an extraordinary size, yet, with the ex- 

 ception of those of the fissirostral types, they are always 

 round ; and it is well known that these fishes keep near 

 to the shore, and live near the ground. There are some 

 singular modifications of the rounded pectoral, which 

 deserve particular notice ; for they are either, 1 . partially 

 cleft ; 2. digitated ; or, 3. very broad at their base, and 

 extended under the throat. Examples of the first 

 are seen in the genera Lepidopus and Cheilodactylus, 

 and in a very few others, where the middle rays are 

 shortest, so that the fin appears lobed in the middle ; 

 but in the last named genus, some of the lower rays, or 

 those nearest the belly, are much longer than the others : 

 the fin has thus an appearance of being injured. The 

 pectoral of Cephalocanthus is represented (Cuv. pi. 73- 

 77-)* as being rounded, but divided in the middle, 

 without any diminution in the length of the rays. In 



* I have not had an opportunity of examining this rare fish. 



