Pearson: Fishes of the Rio Beni Basin 
43 
median line and extending some distance upon the caudal rays ; 
in some specimens the single scale is replaced by two smaller 
scales. 
General body color dark brown above, light brown below ; a 
dark lateral band continued to the tip of the middle caudal 
rays; dorsal with a black diagonal band; anal tipped with 
black; a black vertical humeral spot on the third to fifth ver- 
tical row of scales. In life metallic silvery; anal and caudal 
yellow. 
Bryconamericus alfredae Eigenmann MS. 
17327, 37, 36-68 mm., Rio Colorado, Lower Bopi. Sept., 1921. 
17328, 7, 40-48 mm., Popoi River, Upper Beni. Sept., 1921. 
17329, 4, 37-50 mm., Huachi. Aug., 1921. 
17330, 1, 48 mm., Rurrenabaque. Oct., 1921. 
Bryconamericus bolivianus Pearson, sp. nov. Plate X, fig. 4. 
17349, 9 cotypes, 28-48 mm., Rio Colorado, Lower Bopi. Sept., 1921. 
17350, 9, 32-40 mm., Popoi River, Upper Beni. Sept., 1921. 
17351, 1, 32 mm., Rio Iniqui, Upper Beni. Sept., 1921. 
Head 4 to 4 1/3 ; depth 4 1/3 to 5 ; D.10 ; A. 15 to 16 ; eye 3 
to 3 1/3; scales 4 — 35 to 38 — 2 y 2 or 3; slender, compressed; 
ventral and dorsal outlines evenly arched ; second suborbital in 
contact with the preopercle below, leaving a large naked area 
behind; interorbital convex, its width less than the orbital 
length; frontal fontanel narrow, % the length of the eye, the 
parietal fontanel 11/2 times as long and 3 times as wide at its 
widest point ; occipital process short, its length equal to about 
% of the distance from its tip to the origin of the dorsal ; all 
teeth tridentate; maxillary with 4 or 5 teeth; 4 teeth in the 
inner series of the premaxillary, 3 or 4 teeth about the same 
size in the outer series ; mandible with 4 teeth of the same size 
followed by 4 or 5 teeth regularly decreasing in size; lateral 
line complete ; origin of the dorsal equidistant from the tip of 
the snout and the base of the caudal, its margin truncate ; pec- 
torals reaching base of the ventrals ; ventrals not reaching the 
anal ; anal slightly emarginate ; an enlarged scale at the base of 
each caudal lobe. 
A silvery lateral band, dark beneath the scales, ending at 
the base of the caudal in a small dark spot which is not con- 
tinued on the middle caudal rays, no humeral spot ; chromato- 
phores on the back collected in a single band in the middle of 
each scale. 
