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• / V 340 



unbranched rays. Adipose fin with a large, round, black spot in the center, 

 occasionally extending over most of fin. Caudal fin with a broad wishbone-shaped 

 spot beginning at the base and extending onto each lobe, often merging with a broad 

 black submarginal band in each lobe, thus giving the appearance of being mostly 

 black except for the fin margins and a triangular whitish or yellow spot in the center. 

 Anal fin with a series of smaller brown spots similar to, and in some cases 

 contiguous with, those on the sides of the body. Paired fins very deep black, 

 generally uniform in intensity except for a thin, yellowish distal margin on 

 unbranched (outermost) ray, but distinctly mottled in some specimens. 



Distribution 



Known at present only from isolated locaUties in the Essequibo and 

 Corantijn Rivers, Guyana and Surinam, the upper Amazon basin in Peru, and the 

 middle Parang River in Argentina. These widely disjunct records are presumably 

 indicative of a widespread distribution throughout central and northeastern South 

 America. The low number of voucher specimens deposited in collections may 

 reflect a combination of natural rarity, poor collecting efforts in appropriate 

 habitats, or, possibly, inadequate collections of juvenile ^4. brevifilis as discussed 

 below. 



Ecology 



No ecological information about ^4. marmoratus has been published. The 

 following notes were provided by R. E. Schmidt (personal correspondence) 

 concerning collection of a single specimen of ^4. marmoratus from Whyape Creek, 

 Guyana, near its confluence with the Cuyuni River. At the point where this 





