44 
Indiana University Studies 
Bryconamericus hemigrammus Pearson, sp. nov. 
17353, 11 cotypes, 25-40 mm., Popoi River, Upper Beni. Sept., 1921. 
Head 4 to 4.3; depth, 4.2 to 4.7; D.10; A. 15 or 16; eye 2.8 
to 3; scales 4-34 to 37-21/2 ; interorbital equal to the eye; 
second suborbital in contact with the preopercle below, leav- 
ing a wide naked area behind; occipital process equal to i/8 
the distance from its tip to the origin of the dorsal, bordered 
by 2 scales on the sides; skull not strongly convex; frontal 
fontanel triangular, not half as long as the parietal ; snout 
blunt; 9 gill rakers on the lower gill arch; maxillary % the 
length of the eye, with 2 polycuspid teeth; 4 teeth in the 
inner series of the premaxillary; 3 or 4 tridentate teeth in 
the outer series ; mandible with about 10 three- or five-pointed 
teeth regularly decreasing in size backward; lateral line in- 
complete, the last 5 to 10 scales without pores; origin of the 
dorsal slightly nearer the tip of the snout than the base of 
the caudal; pectorals not reaching base of ventrals, ventrals 
not to anal ; a much enlarged scale at the base of each caudai 
lobe. \ 
A silvery lateral band ; a small caudal spot not continued on 
the middle caudal rays; an indistinct humeral spot. 
Acrobrycon Eigenmann & Pearson, gen. nov. 
Type Tetragonopterus ipanquianus Cope. 
Closely allied to Hemibrycon, differing in that the male has 
a large caudal pouch. In this respect it resembles Argopleura, 
which differs from Bryconamericus by the male possessing a 
caudal pouch. The scales are continued along the middle of 
the caudal much farther than above or below. Along the 
ventral edge of the caudal they are continued only half as 
far. The scales of the lower half of the caudal are attached 
to skin, which is free from the caudal rays it covers and 
which is pouched out away from the rays. Cheek entirely 
covered by the suborbital. Premaxillary with 2 rows of teeth, 
4 in the inner row ; maxillary with teeth along more than half 
its length. 
Acrobrycon ipanquianus (Cope) . 
17305, 3, 72-114 mm., Espia. July, 1921. 
