40 PROCEEDINGS OF THE NATIONAL MUSEUM vol. ii9 



to 30 (usually 29). Lateral-line scales 3 to 5, usually 4. Scales in 

 a median series in front of dorsal fin 11 to 13, usually 12. Total 

 number of vertebrae 38 to 39 with 21 precaudal and 17 to 18 caudal 

 vertebrae. 



Color in alcohol. — Specimens from British Guiana, SU 50446, 

 have the following colors: (The paratypes are coated rather hea\Tly, 

 apparently with lead oxide from a metal number tag, but agree well 

 with the description below.) Top of head light to dark brown. 

 Primary horizontal stripe extending from snout tip and lower jaw 

 posteriorly over maxillary, first and second orbitals, and onto eye. 

 From posterior part of eye, primary horizontal stripe extending to 

 posterior edge of opercular bone. On body, primary horizontal 

 stripe continuing from under fleshy opercular flap posteriorly through 

 fourth scale row and part of fifth to caudal peduncle and caudal fin; 

 on caudal peduncle extending over ventral body sm-face. On caudal 

 fin, primary horizontal stripe not taking form of a narrow wedge but 

 expanding to cover upper part of lower caudal lobe. 



Above primary horizontal stripe a pale stripe extending from snout 

 tip to caudal base. Dark area on sixth through eight vertical scale 

 rows. Aggregation of melanophores on pale stripe vertically above 

 anal fin. Secondary horizontal stripe apparently absent; entire 

 dorsum above middle of second horizontal scale row light brown. 

 Belly silvery, but posterior to pelvic fins in males becoming dusky. 

 Pectoral fins translucent. Dorsal fin sHghtly dusky anterodistally 

 but otherwise translucent and pelvics clear except for dusky distal 

 band. Upper lobe of caudal fin slightly dusky. Anal fin translucent; 

 in some specimens last ray black. 



Color in life. — The colors of aquarium specimens, SU 50246, 

 from Demerara River, British Guiana, are as follows: Dorsal and 

 pectoral fins hyaline. Pelvic fin of male with proximal one-thu-d to 

 three-fourths of fourth to ninth pelvic rays orange red. These fins 

 hyaline in female. Distal one-third of third through fourth pelvic 

 rays and adjacent membrane silvery blue in both sexes. Anal fin 

 of female hyahne with occasionally one spot of silvery blue on distal 

 one-fourth of foiu-th anal fin ray. Male also with silvery blue disposed 

 in same manner but proximal one-third to one-half of all anal fin 

 rays bright red. Proximal portions of caudal fin lobes red above and 

 below extension of primary horizontal stripe on fin rays. These 

 areas silvery yellow with faint indications of red in females. Primary 

 horizontal stripe black. Above this stripe a narrow silvery band and 

 above this body shades to light or sometimes brown on dorsum. 

 Metallic-red spot near anterior narial opening. Belly and sides 

 below primary horizontal stripe white. 



Remarks. — So far as is known Poecilobrycon harrisoni is restricted 



