89. STYGOGENES. 22'3 



tral fins inserted just below the extremity of the pectoral, m the 

 vertical from the origin of the dorsal. Brown, dotted with black. 

 Andes of Western Ecuador. 



a-d. From Mr. Fraser's Collection. 



89. STYGOGENES. 



Adipose fin short (with or without a spine) ; dorsal and anal short ; 

 the outer fin-rays somewhat thickened and rough. Teeth small, 

 slightly curved, notched at the apex, forming a narrow band in each 

 jaw ; palate toothless ; cleft of the mouth of moderate width, with 

 a maxillary barbel on each side ; a short broad flap on each side 

 between the nostrils ; lower lip very b^oad, pendent. Eyes small, 

 covered with transparent skin. Head covered with soft skin. Gill- 

 openings not extending downwards to the throat, separated by a 

 broad isthmus. Ventrals six-rayed, inserted below the dorsal. 



I establish thi-o genus on a few very small fishes collected by the late 

 Madame Pfeiffer, and evidently very similar to the Pimelodus cyclopum 

 of Humboldt. Indeed it is possible that they belong to that species, 

 which is so much coveted by zoologists, and the history of which is 

 still veiled in obscurity. The descriptions by Humboldt are extremely 

 vague, and want the precision and detail requisite for the determina- 

 tion of species ; and the figures illustrating them arc below mediocrity, 

 conveying little more than the general size and shape. Therefore, 

 when Valenciennes (xv. p. 326) extols the exactness of the figures 

 and descriptions of the fishes discovered by Humboldt, we must 

 consider it as a tribute to the " tendre amitie que M. de Humboldt 

 a pour moi," &c, rather than as consistent with fact. 



The most important difference between our specimens and the 

 Pimelodus cyclopum is in the structure of the adipose fin, which is 

 supported by a small, stiff, rough spine in our specimens, as in Hy- 

 postomus. No such spine is visible in the figure given by Humboldt. 

 But I would not affirm that this is really a specific difference, as it 

 may have been overlooked by him. In other respects the fishes 

 agree, as far as we can judge from the monstrous figure. 



Madame Pfeiffer was not very accurate with regard to the localities 

 whence she obtained the species which she collected. Thus, our 

 specimens are marked as being from the Azores ; of course it is much 

 more probable that she obtained them during her travels in the 

 Andes ; perhaps she had some knowledge of the celebrated fish of 

 Humboldt, and inquired for it. 



It remains doubtful, therefore, whether our specimens arc identical 

 with Pimelodus cyclopum or not. The error of describing them as 

 distinct will be less than that of confounding them. If they be dis- 

 tinct, we should consider the new species as the type of the genus. 



1. Stygogenes humboldtii. 

 B. 4. D. 6-1. A. 6. C. 13. P. 8. V. 6. 

 In general form very similar to Arges. The head is as broad as 



