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PROCEEDINGS OF THE NATIONAL MUSEUM 



from Baduel, French Guiana, SU 50259, and specimens from Uruard 

 Brook, SU 50257, have all the cusps of the premaxillary teeth about 

 equal (fig. 2). Specimens from Obidos have the second cusp from 

 posterolateral side much enlarged, quite similar to the upper left tooth 

 shown in the figure of Poecilobrycon egues (fig. 12)]. Maxillary with 

 single uni- to octocuspid compressed tooth, cusps subequal. Dentary 

 with 5 to 6 teeth (almost always 6 in all population samples examined). 

 Teeth in anterior dentary tooth row quinque- to sexcuspid (usually 

 sexcuspid). Specimens from Uruara Brook with subequal cusps; 

 however, specimens from Obidos mth centralmost cusp enlarged in 

 anterior 4 to 5 teeth of dentary. Teeth 2 to 6 in inner tooth row of 

 dentary (seen in alizarin preparations only). Gill rakers 9 to 104-17 

 to 18 (seen in alizarin specimens only). 



Figure 2. — Nannostomus beckfordi, male, SL 30.0 mm., SU 50261 (both scales are from 

 third longitudinal row, below dorsal fin). 



Dorsal fin ii,8; anal fin iii,9; pectoral i,10 to i,12; pelvic fin ii,7. 

 Adipose fin absent in all specimens examined. Principal caudal fin 

 rays 10/9; distal tips of all elements of first 10 rays contained in upper 

 caudal lobe, distal tips of remaining 9 principal rays in lower lobe. 

 Male with anal fin (figs. 2 and 4) somewhat modified in same manner 

 as extremely modified anal fin of N. digrammus. Anal fin of female 

 (fig. 3) unmodified. [Observation of living male beckjordi shows 

 that while courting and spawning, the male often cups the fin into a 

 spoon-shaped bowl and that, while spawning, the male places his fin 

 partially over the female's vent.] 



For radial grooves of scales in median scale row below dorsal fin, 

 see figure 2. Posterior field with 2 to 6 radial grooves; dorsal and 

 ventral fields with 1 or 2 radial grooves; and anterior field with 3 to 



