THE AMERICAN TETRAGONOPTERINAE. 179 
Occipital process 4 to 5 in the distance from its base to the dorsal; bordered 
by two and five tenths to three scales. Interorbital almost flat. Frontal fon- 
tanel much narrower than the parietal, two thirds as long as the parietal without 
the occipital groove. Second suborbital broad, in contact with the preopercle 
at its middle and below, leaving a narrow naked margin behind it, third sub- 
orbital narrow, inconspicuous. Mouth small; snout short. Maxillary shorter 
than the eye, mandible a little longer. Premaxillary with five, 3- and 4-pointed 
teeth in the inner row; two tricuspid teeth in the outer row. Maxillary with 
two or three small tricuspid teeth placed close together. Dentary with a 
graduated series of five large 3- to 5-pointed teeth followed by five or six 
minute conical ones on the sides. 
Gill-rakers 7 + 11. 
Anal sheath short, of about 6 scales, covering the bases of the first 5 rays. 
Lateral line developed on 5 scales. 
Origin of the dorsal equidistant from the snout and caudal, penultimate 
ray 2 in the longest ray, which is 3.5 in the length. Origin of the anal on the 
vertical from the fifth or sixth dorsal rays. Anal long and wide, the rays of 
nearly the same length throughout. Origin of ventrals on the vertical from the 
third or fourth scale in front of the dorsal. Ventrals reaching to or beyond the 
origin of the anal, pectoral barely reaching the ventrals. 
Entire dorsal black, with never more than the narrow base and extreme 
tips of rays whitish. One half to one fifth of the anterior seven anal rays, the 
tips of all the middle ones and almost the entire last five rays black. A heavy 
black vertically elongate humeral spot crossing the fourth, fifth, and sixth 
scales of the lateral line series. No caudal spot. Seales of the dorsal surface 
outlined with dusky. 
In the type of H. melanopterus the ventrals reach considerably beyond 
the origin of the anal, and the anal is more conspicuously marked with black 
than in the other specimens. 
4. HyYPHESSOBRYCON MINOR Durbin. 
Plate 22, fig. 3. 
Hyphessobrycon minor Durpin, Ann. Carnegie mus., 1909, 6, p. 65 (British Guiana); ErGenMANN, 
Rept. Princeton univ. exped. Patagonia, 1910, 3, p. 436; Mem. Carnegie mus. 1912, 5, p. 339, pl. 
49, fig. 5. 
Hapirat.— British Guiana. 
