36 
Indiana University Studies 
lower jaw radially arranged on the edge of the flat distal part, 
margin of the side of the mandible raised, at right angles with 
the margin of the distal part, with about 8 conical or triden- 
tate teeth ; anal short. 
Very closely related to Parecbasis, from which it differs by 
having teeth on the maxillary and sides of the lower jaw. 
Prodontocharax melanotus Pearson, sp. nov. Plate XII, figs. 
1 and 2. 
17331, 53, 36-54 mm., Tumupasa. Dec., 1921, about 1,000 ft. 
17332, 3, 48-52 mm., Eurrenabaque. Oct., 1921, about 1,000 ft. 
Head 4 to 4 1/3 ; depth 3.2 to 3.66 ; D.ll ; A. 15 to 18 ; eye 
2% to 3; scales 6 — 34 to 37 — 3 or 4; dorsal and ventral pro- 
files equally curved ; eye about equal to the snout, less than the 
4. Dentition of Prodontocharax melanotus Pearson 
interorbital; teeth on the maxillary-premaxillary border con- 
tinuous; snout truncate; third suborbital large, in contact 
with the preopercle below but not in contact behind; post- 
orbitals not extending to the preopercle, weak; fontanel 1.5 
times as long as the eye ; gill rakers slender, 1/2 as long as the 
diameter of the eye; about 17 on the lower gill arch; pseudo- 
tympanum present, predorsal area narrowly rounded, scaled; 
origin of the dorsal nearer to the tip of the snout than to the 
base of the caudal, its margin truncate ; pectorals usually not 
quite reaching the base of the ventrals, in a few specimens just 
reaching the base of the ventrals ; ventrals not reaching anal ; 
anal slightly emarginate ; depth of the caudal peduncle 1 y% 
times in its length. 
Dorsal with a large black irregular spot extending over 
about the first 5 rays and interradial membranes ; caudal spot 
