NO. 3538 CHARACID FISHES — WEITZMAN 43 



of teeth in the dentary; in addition, it may be distinguished by the 

 following combination of characters: Adipose fin present; 33 to 34 

 vertebrae; 2 to 5 perforated scales in the lateral fine; iii,9 anal fin 

 rays; 9 + 14 gill rakers and 28 to 30 scales in a lateral series. 



Description. — Body elongate, slender, and somewhat cylindi-ical 

 anteriorly, but sides somewhat flattened; compressed posteriorly. 

 Greatest depth anterior to dorsal fin and posterior to distal tips of 

 appressed pectoral fins. Standard length of largest specimen 38.3 

 mm. Greatest body depth 5.0 (4.7-5.3) ; least depth of caudal 

 peduncle 10.4 (10.0-11.2); length of caudal peduncle (including both 

 sexes) in specimens listed below from Brazil 6.9 (6.7-7.5) and from 

 British Guiana 6.2 (6.0-6.6); snout tip to origin of dorsal fin 1.9 

 (1.8-1.9); snout tip to origin of anal fin 1.2 (1.2-1.3). 



Head elongate, somewhat depressed, especially over snout. Top 

 of head slightly convex between eyes. Snout rounded in horizontal 

 profile. Head 3.9 (3.9-4.0); eye in head, Brazilian specimens 3.0 

 (2.8-3.2), British Guiana specimens 3.4 (3.2-3.4); snout in eye 1.0 

 (0.9-1.2); least width of bony interorbital in greatest eye diameter 

 1.1 in all specimens from Brazil and 1.0 in all specimens from British 

 Guiana. 



Premaxillary with 6 to 7 quinquecuspid teeth. Posteriomost lateral 

 tooth sometimes with only 3 to 4 cusps. Each maxillary with 1 

 quadricuspid tooth. Dentary with 6 or 7 quinque- or sexcuspid 

 teeth, cusps subequal. Second row of dentary absent in all alizarin 

 specimens. Gill rakers 9+14. 



Dorsal fin rays ii,8; anal iii,9; pectoral i,9 to i,ll; pelvics ii,7. 

 Adipose fin present in all specimens examined. Caudal fin with 

 principal rays 10/9. Distal tips of 8 principal rays in upper lobe and 

 11 in lower lobe. 



Anal fin of males slightly modified. Male specimens examined from 

 Venezuela and Brazil mth anal fin shape as shown in insert in figure 11. 

 This shape approaches that of anal fi^n of Poecilobrycon eques but fin of 

 P. unifasciatus not as large. Second undivided ray expanded anteriorly 

 and posteriorly, giving this ray a flattened appearance. Posterior 

 margin of this ray fits into recess formed by 2 ray halves of expanded 

 and flattened third unbranched ray behind. First branched ray with 

 slight recess for the enlarged third ray. Inclinator muscle only slightly 

 developed and beyond basal scales attached to ninth ray only. 

 Specimens from British Guiana with anal fin of male less developed 

 than specimens from Brazil and Venezuela. Anal fin of specimen 

 from British Guiana resembles that of entire specimen in figiu-e 11. 

 Second and third unbranched and first and second branched rays only 

 slightly enlarged. Anal fin of female from British Guiana, Brazil, and 

 Venezuela wdth rays not at all enlarged. Male specimens from Brazil 



