■v.■:":-■"■■'^^:.' • "■-,■/ ■':":'^ 183 



5a (4b). Size large, adults commonly exceeding 200 mm SL, Swimbladder generally 

 small (< 10% SL in longitudinal length), encapsulated in a pyriform or heart- 

 shaped bony ossification of the complex centrum (except in A. pardalis). '<■■ Vf 

 Pigmentation often consisting of one or more distinct stripes along body, and/or 

 prominent, irregular blotches on top of the head and along the entire length of 

 the back 6. 



5b. Size small, adults rarely exceeding 200 mm SL. Swimbladder very large and not 

 encapsulated by bone, with a slightly turgid anterior chamber, and usually with 

 two fleshy caecae on posterior margin. Pigmentation either plain or with diffuse 

 spotting, but never with large, irregular blotches on top of head and back 10. 



6a (5a). Anal fin rays 41-50. Head very spatulate, snout moderately pointed in 

 dorsoventral profile. Mouth strongly inferior. Countershaded pigmentation, 

 ranging from a narrow, thin brown or gray stripe along dorsum, to uniform 

 brown shading over most of sides; never strongly mottled or heavily spotted. 

 Total gill rakers on outside row of first arch 18-25, long, strongly crenulate on 

 medial margin Ageneiosus ucayalensis. 



6b. Anal fm rays rarely greater than 40. Head shape variable, ranging from broadly 

 rounded to slightly pointed in profile. Mouth weakly to moderately inferior. 

 Pigmentation variable, but body and head usually prominently mottled, speckled, 

 or striped. Total gill rakers on outside row of first arch less than 18, moderately 

 long, crenulated on medial margin , 7. 



7a (6b). Total vertebrae behind complex centrum, including the preural centrum, 

 38-42. Distribution in the Orinoco and/or Amazon river basins 8. 



