■,■'■ .'3-., 268 



Distribution 



Ageneiosus n. sp. ranges widely throughout the middle and lower Amazon 

 basin, including substantial portions of the Rio Negro, Rio Trombetas, Rio Punis, 

 and Rio Tapajos (Fig. 48). It is also present in the Rio Amapd, which drains directly 

 into the Atlantic Ocean, north of Ilha de Maraj6 at the mouth of the Amazon River. 

 Additional collecting is needed to determine the extent of the species' distribution 

 within other coastal drainages and tributaries of the Amazon. With the exception of 

 one specimen taken from the Rio Casiquiare drainage in Venezuela, all of the 

 material examined was collected in Brazil. 



\,^^^^'^ \ '\a. ,.:■. \' . • ■ V .'f - ■ 



Ecology •'^ . I , . . 



-*''. K ^ '. i »■■■:- y 



Nothing previously published. The material examined included a 

 preponderance of nuptial males (N = 45), ranging in size from 100-147 mm SL, and 

 all collected between February and June. Only one gravid female (168 mm) was 

 : found in these collections, suggesting that there might be possible segregation of the 

 sexes, a skewed sex ratio, or gear selectivity during sampling (nuptial males are 

 probably captured more easily with gill nets or similar gear, due to their spiny 

 barbels and dorsal fin). Three other non-gravid females ranged in size from 141- 

 165, indicating that females probably reach a slightly larger size than males. 



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Comments 



Some authors have apparently confused^l. n. sp. withy4. vittatus, presumably 

 on the basis of some overall similarity in coloration patterns. The description oiA. 

 vittatus by Steindachner (1908) was accompanied by a drawing of the holotype, 

 which exhibits a pronounced midlateral stripe similar to that found inA.n. sp. 



