182 



3a (2b). Head and body heavily marbled, pigment consisting of prominent, large, 

 dark black blotches and spots. Coloration on body not uniformly countershaded. 

 Paired fins nearly uniform black or with broken stripes over interradial 

 membranes. Caudal fin with a large triangular black patch encircling a lightly 



pigmented central spot. Blotches on sides extending onto anal fin Ageneiosus 



marmoratus. -i - ' 



3b. Head and body not heavily marbled. Coloration on body countershaded, the 

 upper half typically slate gray, diminishing in intensity below midline. Paired 

 fins often striped or mottled, but never uniformly black. Caudal fin without 

 large dark black blotches, with a narrow black band on distal margin. Anal fin 

 pale; pigment, if any, confined to dark black marginal band ..Ageneiosus brevifilis. 



4a (lb). Caudal fin weakly forked to strongly emarginate, with broadly rounded 

 lobes. Most of tail darkly colored, but tips of lobes unpigmented, appearing 



v white or yellow. Color on body and fins dark purplish to black, with numerous 

 ^- small, irregularly shaped black spots on sides and top of head and body. Size 

 large, adults commonly exceeding 250 mm SL. Swimbladder small, encapsulated 

 by bone. Distribution limited to the Rio Negro dxdXndigt.... Ageneiosus poly stictus. 



4b. Caudal fin strongly forked, with sharply pointed lobes. Tail coloration variable, 

 often pigmented and slighly mottled, but never appearing uniformly dark 

 throughout and with tips of lobes immaculate. Color on body variable, with or 

 without spots, but rarely appearing dark black. Adult size small or large. 

 Swimbladder encapsulated or not encapsulated 5. 



■J «A- ■-.■ 





