Pearson : Fishes of the Rio Beni Basin 
51 
ORDER CYPRINODONTES. 
Family PcEClLiXMk 
Rivulus rogoaguae Pearson & Myers, sp. nov. 
17257, type and 41 paratypes, the largest the type, 28-54 mm., Lake 
Rogoagua. Nov., 1921. 
Closely related to R. balzanii from which it differs in the 
lesser depth. 
Head 3.2 to 3.53 ; depth 5 to 5.65; D.8; A.16 to 20; eye 3 to 
3.6; scales 35 to 41 in a lateral series, 11 in a transverse 
series between the dorsal and the anal, 28 to 31 predorsal; 
head rather flattened, much depressed above, little or not at 
all bulging at the sides, slightly sharper and less rounded in 
profile than in most other species, lips rather thinner, the 
lower projecting; head 14/2 as long as wide and 13/5 as long 
as deep ; eye 1 1/3 in the interorbital, equal to the snout ; inter- 
orbital 1 1/3 in the head, equal to the least depth of the caudal 
peduncle; body more or less rounded anteriorly; dorsal in- 
serted over the middle of the anal, its origin twice as far 
from the preopercle as from the caudal base ; anal base ending 
very slightly in advance of the end of the dorsal base, its 
origin midway between the caudal base and opercle edge at 
the height of the pectoral insertion; pelvics originating a 
snout length nearer to tip of the snout than to the caudal 
base, scarcely reaching or reaching vent; pectorals slightly 
more than reaching pelvics. 
Color yellowish brown, darker above, belly pale yellow; on 
the fourth lateral scale row (counting down from the dorsal) 
each scale has a brown dot, every third or fourth dot darker 
than the rest; similar rows on the sixth and eighth rows; 
there is almost an obsolete row on the tenth series; anal fin 
with 3 series of dark dots, one on each fourth ray; dorsal 
similarly marked ; caudal clear or slightly clouded. 
Rivulus strigatus Regan. 
17258, 61, 30-42 mm., Lagoons, Lake Rogoagua. Nov., 1921, 
17259, 103, 24-40 mm., Ivon. Feb., 1922. 
17260. 1, 36 mm., Reyes. Nov., 1921. 
