92 Evcrmann and Kendall Fish from Central Ecuador. 



Recognizing Regan's classification, our specimens would 

 represent his species. However, for reasons appearing further 

 on in this paper, we are convinced that Cydopium cydopum is 

 the valid name for them. 



Our collection contains specimens representing both the 

 eastern and western slopes of the Andes, but from very closely 

 neighboring localities. These specimens exhibit considerable 

 variation among themselves and show that previous descriptions 

 have been not wholly accurate. The discrepancies indicate that 

 certain changes in the present arrangement of the genera and 

 species are necessary and suggest the possibility that future in 

 vestigations may necessitate still further modifications in our 

 views of the whole family. 



In the present paper we present at some length the data 

 which these specimens furnish and indicate the conclusions to 

 which they point in the thought that this will prove of use to 

 others who may have occasion to study these fishes. 



CLASSIFICATION AND SYNONYMY. 



The classification adopted by Eigenmann and Eigenmann is 

 based upon the descriptions by previous authors and a few 

 specimens of Cydopium cydopum in the Museum of Comparative 

 Zoology at Cambridge, which we also have been privileged to 

 re-examine, through the kindness of Prof. Samuel Garman. 

 Eigenmann and Eigenmann include three genera in the Argidse, 

 which they separate as follows : 



a. Adipose fin a long, low fold of skin which gradually merges into the 

 dorsal profile anteriorly and posteriorly ; lower lip very broad. 



Arges. 



aa. Adipose fin short, with a spine placed near the tail. Cydopium. 



aaa. Adipose and ventral fins wanting. Astroblepus. 



Under the genus Arges, they place Arges sabalo of all previous 

 writers ; Brontes prenadilla Cuvier & Valenciennes ; Arges pre- 

 nadilla, Steindachner ; Arges brachycephalus Giinther ; Arges 

 longifilis Steindachner ; and Arges peruanus Steindachner. 



In the genus Cydopium are the one form which has borne the 

 various names, Pimelodus cydopum Humboldt ; Stygogenes 

 cydopum, Giinther ; Cydopium cydopum, Putnam ; Cydopium 

 humboldtii Swainson ; Stygogenes humboldtii, Giinther ; and the 

 additional species, Stygogenes guentheri Boulenger. 



