ANAL FIN. 29 



often excessively prolonged, and ending in spatulate or 

 thread-like filaments. This sudden elongation of the 

 first two or three rays we shall term falcate ; and it is 

 particularly observable that this shape occurs in nearly 

 all genera which represent the tribe of Gymnetes in 

 their own circle. Nevertheless, the secondary modi- 

 fications of this fin are so numerous, that to describe 

 them all in this place would be tedious and unne- 

 cessary. Among the eels, the dorsal is always simple 

 and undivided, narrow, and of equal breadth throughout; 

 and this occurs in almost ail the representatives of the 

 apodal order, as Lepidotus, Ammodytes, Cepola, and Ophi- 

 dium, among the Gymnetes; Blennius, Anarhichas, 

 &c. in the Gobiadce ; Chimera, in the cartilaginous 

 order ; and Ophiocephalus, among the Macroleptes. In 

 most of these the dorsal fin unites with the caudal, 

 as in the eels and other Murcenidce ; while in the Blen- 

 nidce, or blennies, there is a small interval between them. 

 Lastly, we may notice the long fleshy filaments which 

 in some few genera surmount the spinous rays of the 

 dorsal fin, and produce a very singular appearance. 

 These appendages are mostly found among the Zeidce, 

 or sun-fish, of which the common dory of our coasts is 

 a striking example. 



(32.) The anal fin may be termed symmetrical to 

 the dorsal ; or, at least, its situation on the under part of 

 the tail is analogous to that of the dorsal on the back. 

 It must be observed, however, that this fin is always 

 placed behind the vent, so that the length of the tail, 

 in many cases, is indicated by the length of the anal 

 fin. It is subject to very little variation in form, and 

 still less in construction, for it generally corresponds 

 with the hinder part of the dorsal : it is almost always 

 nearly the same breadth throughout, and without any 

 particular variation in other respects ; all the rays, 

 except the two or three first, which are more or less 

 spinous in the most perfect families, are articulated and 

 branched. The anal fin is most developed in the apodal 

 order and its representatives, where we have it some- 



