156 THE AMERICAN CHARACIDAE. 
very little longer than the head. Origin of anal on the vertical from the last 
dorsal ray. Anal deeply emarginate, the longest ray 1.25 in the anal base. 
Ventrals on the vertical from the first scale in front of the dorsal. Ventrals 
reaching the second to fourth anal ray. Pectorals reaching to the first scale 
in front of the ventrals or to the second scale behind the ventrals. 
No humeral spot. Caudal spot not quite as wide as the caudal peduncle, 
but extending from the tips of the middle caudal rays to the vertical from 
one of the last five anal rays, more diffuse at the anterior end. Lateral stripe 
very faint, heavily overlaid with silvery. Fins all a little dusky. Scales of 
the back outlined with dusky. Cheeks and sides below the lateral stripe with 
bluish iridescence. 
14. HemicrRaMMus TRIDENS Eigenmann. 
Plate 19, fig. 2; Plate 78, fig. 4. 
Hemigrammus tridens E1GENMANN, Proc. U. S. N. M., 1907, 83, p. 15 (Arroyo Pypucu); Rept. 
Princeton univ. exped. Patagonia, 1910, 3, p. 436. 
Hapirat.— Arroyo Pypucu, Paraguay. 
Specimens examined. 
Catalogue Number of 
number specimens Size in mm. Locality Collector 
11262 I. Type 1 20 to base of Arroyo Pypucu, Paraguay Anisits 
, caudal 
11262a I. 2 17, 18 to base Arroyo Pypucu, Paraguay Anisits 
of caudal 
Head 3.4; depth 3; D.11; A. 16-19; scales probably 4 to 5-30 to 35-3; 
eye 2.4 in head, interorbital 3+ in the head. 
Compressed, depth of head at the base of the occipital process 1.75 in the 
greatest depth. Preventral region rounded without complete series of median 
scales. Predorsal region rounded or very slightly keeled, with complete regu- 
lar series of 11 scales. 
Occipital process 6 in the distance from its base to the dorsal, bordered 
by 2-2.25 seales. Interorbital slightly convex. Frontal fontanel triangular, 
its base narrower than the parietal and half as long as the parietal without 
the occipital groove. Second suborbital in contact with the preopercle. Snout 
short, mouth large; maxillary shorter than the eye, 3 in the head. Mandible 
about equal to the eye. Premaxillary with an inner row of five teeth, with 
5 long points, the middle one much the longest, the outer row with two nar- 
