94 Evermann and Kendall Fish from Central Ecuador. 



ray, the short upper rays of this fin being completely surrounded by it. A 

 puffed fold of skin surrounds the lower short rays of the caudal. 



Referring to Arges longifilis (1. c., p. 20), he says: 



The fold of skin on the back is in some more, in others less, fleshy, and 

 of equal height and length with A. sabalo; 



and regarding some very small examples, 4.5 to 5.5 cm. long, 

 he further remarks : 



The fold of skin on the back is very distinct throughout its length, and 

 very thin. 



Concerning Arges prenadilla, he says, on this point : 



A plainly visible seamlike fold of skin on the back begins over and a 

 little in front of the anal and extends to the caudal, uniting with the 

 upper ray of the fin. 



In another place he states : 



In my opinion Giinther's species of Arges brachycephalus is identical 

 with Arges prenadilla, 



and he goes on to say regarding three examples (male and 

 female) which he believes to be the same species, from Peru, 

 measuring 4.5, 5 and 9 cm. : 



The two little specimens are especially noteworthy in that they show 

 not the slightest trace of the adipose fold, but as to depression and form of 

 head they correspond almost exactly with 7 cm. specimens of Arges sabalo 

 previously mentioned. 



However, Steindachner's figures of Arges sabalo and Arges 

 longifilis show a decidedly high and thin adipose fin which, from 

 his description, must be inaccurately represented. Regarding 

 his Arges peruanus, Steindachner says (1. c., p. 21) : 



The adipose fin resembles a long thickish fold in the skin, of slight 

 elevation, gradually losing itself before reaching the caudal ; 



but his figure shows even no trace of such a fold. 



These descriptions show conclusively that what has been so 

 regarded is not a true adipose fin, which conclusion our speci 

 mens substantiate. It is evident that the presence of the sup 

 posed adipose fin on the different species, is simply due to the 

 action of the preservative and that there is no true adipose ; 

 and the smaller the individual and the longer its stay in the 

 preservative, the more like an adipose fin the fold may become. 



