FISH. 



59 



The species of this genus are numerous, and extremely similar to each other. 

 Many of them appear to rest on characters taken simply from the relative lengths 

 and degrees of stoutness of the dorsal and anal spines. This renders it extremely 

 difficult to identify single specimens. Perhaps I am wrong in referring the one 

 described above to the G. Gula of Cuvier and Valenciennes; but it makes so 

 near an approach to that species, that I hardly dare characterize it as distinct. 

 It cannot be the G. Aprion of those authors, which is closely allied to the G. Gula, 

 and is found on the same coasts, since its teeth are so very much finer : the 

 caudal also is not scaled. It is small, but Cuvier and Valenciennes state that 

 none of their specimens of the G. Gula exceed five inches. Mr. Darwin took it 

 in a salt-water lake, Lagroa de Boacica, at Rio de Janeiro. 



2. Gerres Oyena. Cuv. et Val.? 



Gerres Oyena, Owe. et Val. Hist, des Poiss. torn. vi. p. 355. 



Smaris Oyena, Biippell, Atlas zu der Reise im Nb'rd. Afr. Zoologie; p. 11. tab. 3. fig. 2. 



Form. — Greatest depth contained rather more than three and a half times in the entire length: the 

 dorsal curve very regular. Profile above the eyes a little concave. Length of the head exceeding 

 its depth. Maxillary as in the species last described. Suborbital with its lower margin distinctly 

 but not very deeply notched ; not denticulated. Diameter of the eye less than one-third the length 

 of the head. Posterior orifice of the nostrils twice the size of the anterior one. No denticula- 

 tions on any part of the head or gill-cover. A narrow band of velutine teeth in each jaw, of 

 about the same length and degree of fineness above and below ; but none on the palate or 

 tongue. 



The dorsal commences in an exact vertical line with the insertion of the ventrals : the anterior 

 spines are a little arcuate; the first, as in the other species of this genus, is extremely short ; 

 the second and third in this specimen are broken at their extremities so that their exact length 

 cannot be ascertained, but the portion of the second remaining (and of this spine apparently 

 only a very small piece is gone) nearly equals half the depth of the body; length of the fourth 

 spine which is perfect not quite equalling two-fifths of the depth; fifth, sixth, and seventh spines 

 gradually decreasing ; eighth and ninth scarcely shorter than the seventh : the second spine 

 is much compressed, and though obviously stronger than any of those which follow, not nearly 

 so stout as in many other species ; its breadth is not more than one-twelfth of its length. Anal 

 commencing in a line with the fourth soft ray of the dorsal ; the second spine compressed 

 similarly to the second dorsal spine, and of about the same degree of stoutness, but its length 

 one-third less, being just equal to one-third the depth of the body ; the third spine scarcely 

 shorter than the second, but much slenderer; the soft rays gradually decreasing from the first, 

 which is a little shorter than the third spine, to the last but one, the last itself slightly prolonged 



