290 FISHES OF WESTERN SOUTH AMERICA 
The Amazons 
15824, 17, 105-172 mm., Lago Sanango, Allen, November, 1920. 
15834, , , Rio Paranapura, Allen, November, 1920. 
15838, 15, 112-140 mm., Rio Nanay, Allen, September, 1920. 
17846, 65, 66-140 mm., Lago Cashiboya, Allen, August, 1920. 
17847, 2, 120 and 127 mm., Rio Ucayali, Orellana, Allen, August, 1920. 
17849, 5, 67-108 mm., Rio Ucayali, Contamana, Allen, August, 1920. 
17852, 1, 113 mm., Iquitos, Allen, September, 1920. 
The ripe females are of much deeper form than the males. The depth con- 
tained in the length of two individuals which were about equal in length: #3 
Qg 2.15; in number 15838, depth 2.36-3.40. 
Some individuals have a dark area near the extremity of each caudal lobe, 
others not. Dorsal truncate, the longest ray of the depressed fin extending beyond 
the tip of the last; anal truncate; preventral area rounded; air bladder extending 
to the posterior end of the anal fin; origin of the dorsal midway between end of 
snout and tip of adipose fin; origin of ventrals nearer end of snout than to the 
origin of the caudal fin. 
383. PSECTROGASTER CISANDINUS Allen, sp. nov. 
Plate XIV, fig. 3 
15834, 1, 185 mm., Rio Paranapura, Allen, November, 1920. 
15837, 2, 102 and 106 mm., Rio Nanay, Iquitos, Allen, September, 1920. 
17850, 3, 67-146 mm., the largest the type, Iquitos, Morris, 1922. 
17851, 2, 102 and 103 mm., Lago Cashiboya, Allen, August, 1920. 
15842, , , Rio Paranapura, Yurimaguas, Allen, November, 1920. 
Readily separated from the nearby P. amazonicus by the greater fin length, 
the strong lateral keels of the preventral region, the greater general angularity, 
strongly inferior mouth, low lateral line. 
Head 3.0-3.3; depth 2.5-2.7; D. 2.6—2.8 in the length, rays 10-11; A. 13-14; 
scales 10-14, 538-55, 6; eye 3.0-3.3; interorbital 2.3. 
Dorsal curvature greater, and not nearly so regular as the ventral; depressed 
above the eye; fontanel furrow long, narrow, less than pupillary diameter; occipital 
process sub-triangular, equal in length to fontanel; predorsal region slightly acute, 
partly with median scales, moderately compressed; dorsal fin shghtly interrupting 
the dorsal line. Venter broad, laterally keeled; postventral moderately trenchant, 
with 8-9 median scales, scales ridged in median line, not spinous; anal slightly set 
into ventral contour. 
Dorsal fin erect, triangular, its last rays one-fourth to one-third the length of 
the first; pectoral variable, sometimes overlapping first fifth of the ventral fin, some- 
times failing somewhat to reach it; ventrals variable, but usually more than reaching 
anus; anal emarginate, its first rays the longest, graduated down; caudal forked 
about half its entire length. 
Snout prolonged, mouth inferior, its width not exceeding snout measured from 
the orbit; without teeth; gill-rakers soft, widely spaced, about ten in each series, 
becoming elongate ventrally. 
