12 
Indiana University Studies 
other fins dark, the ehromatophores collected along the rays, 
the membranes clear. 
Very closely related to N. rosse from Colombia from which 
it differs by possessing a shorter adipose, a higher dorsal, 
longer pectorals, longer barbels, and by a different arrange- 
ment of spots. 
Imparfinis bolivianos Pearson, sp. nov. Plate II, fig. 3. 
17269, 2 cotypes, 54 and 66 mm., Huachi. Aug., 1921. 
Very similar to I. microps in general appearance, but differs 
by having the origin of the ventrals below the origin of the 
dorsal and longer maxillary barbels. 
Head 4.8 and 5; depth 7.25 and 8; D.7; A.13; width of the 
head 1.5 times in its length, its depth 2 and 2 1/3 times; eye 
8 and 9 times in the head, interorbital 4 times, snout about 
3 ; head depressed ; the eyes superior in position, without a 
free orbital margin; lower jaw slightly projecting; maxillary 
band of teeth shorter than mandibular ; no teeth on vomer or 
palatines; maxillary barbels extending to the end of the pec- 
torals, postmentals to their origin; distance of the dorsal 
from the tip of the snout 2.2 and 2.4 in the total length; all 
rays of the dorsal except the last of about equal height; anal 
rounded, its origin slightly in advance of the origin of the 
adipose; caudal deeply forked, the lower lobe the longer, 1.2 
times in the length of the head; adipose 4.25 and 4.5 times 
in the total length ; origin of the ventrals under the origin of 
the dorsal; distance from the tip of the snout to the origin of 
the ventrals 2.4 times in the length. 
Color brown, no markings. 
Rhamdella rusbyi Pearson, sp. nov. Plate II, fig. 4. 
For Dr. H. H. Rusby, leader of the Mulford Expedition. 
17275, type and paratypes, 13, 150-208 mm., Rio Colorado, Lower Bopi, 
Bolivia. Sept., 1921. 
Head 4.5 to 4.75; depth 5.6 to 6.5; D.I.6; A. 12 to 14; width 
of head 1.25 to 1.3 in its length, eye 6.5 to 7, interorbital 4.5 
to 5; snout 2.5 to 2.6; body elongate and slender; dorsal 
spine about 2 times in the head ; pectoral spine slightly longer 
than the dorsal ; the head flat, the entire surface covered with 
skin ; the fontanel extending to the base of the occipital proc- 
ess, which extends 1/3 of the distance to the dorsal spine; 
