16 
Indiana University Studies 
Head 3y s to 3 ? / 3 ; D. 1.6; A. L6; interocular slightly less 
than the distance between the eye and the posterior nostril, 4 
in the head; nasal flap triangular, moderate, not produced; 
barbel in the young extending almost to the gill opening, in 
the older not quite so long; pectoral spine slightly produced, 
extending to the second third of the ventral; origin of the 
ventrals under the first dorsal ray; ventrals extending 2 / 3 or 
% to the anal opening; anal opening about 7/9 of the distance 
between the origin of the ventrals and the base of the anal ; 
anal does not extend to the caudal, second and third rays more 
widely separated in the male ; outer caudal rays produced ; 
adipose fin long, low, weakly developed, without spine; dorsal 
spine V/ 2 times in the head; dorsal spine slightly produced; 
distance from the dorsal to the tip of the snout 2 1 /. i to 2 1/2 
times in the length; outer series of premaxillary teeth more 
or less acute with 3 y-shaped bicuspid teeth. 
Color light brown to dark brown, caudal with black spots, 
base of the caudal with a dark streak. 
Family Cetopsble. 
Cetopsis candiru (Spix). 
17256, 1, 242 mm., Rurrenabaque. Sept., 1921. 
Cetopsis plumbeus Steindachner. 
17255, 10, 74-140 mm., Rio Colorado, Lower Bopi. Sept., 1921. 
Family Pygidiid^e. 
Pygidium rivulatum (C. & V.). 
17096, 34, 32-115 mm., Rio Colorado, Lower Bopi. Sept., 1921. 
17097, 9, 35-72 mm., Popoi River, Upper Beni. Sept., 1921. 
17098, 50, 10-78 mm., Tumupasa. Dec., 1921. 
17099, 106, 24-86 mm., Rurrenabaque. Sept., 1921. 
The above specimens differ from those from the Lake Titi- 
caca basin and the western slope by having the barbels longei 
and the spots not running into vermiculations. The spots dif- 
fer with the altitude. Those from the Rio Colorado have 
either large or small spots ; in some they are placed in lateral 
lines in others they are irregular. Those from Rurrenabaque 
have the spots collected in two lateral lines with the spots 
more or less distinct. Those from Tumupasa have two lateral 
