THE AMERICAN TETRAGONOPTERINAE. 195 
Caudal spot intense black, roundish and scarcely if at all continued on 
the caudal rays. Humeral spot lacking but the intense narrow black lateral 
stripe widened somewhat in the humeral regions. Scales of the back and sides, 
above the lateral stripe, heavily outlined with dusky. All the fins somewhat 
dusky but without distinet black or white markings. Sides over the lateral 
stripe and below it with a steel-blue iridescence. Preopercle also with blue 
iridescence. 
17. HypHESSOBRYCON STIGMATIAS Fowler. 
Hyphessobrycon stigmatias Fowimr, Proc. acad. nat. sci. Phil., 1913, p. 547, fig. 14 (Tributary of the 
Madeira River near Porto Velho). 
This species is known only from the type, 23 mm. long, No. 39231 A. N.S. P. 
Head 3.6; depth 3.6; D. 11; A. 19; scales 33, 9 scales between dorsal and 
ventral; snout 4; eye 2.5, interorbital 2.5 in the head. 
Eleven predorsal scales. Maxillary with three cusps on its upper, anterior 
margin, suborbital nearly covering cheek. 
Seales of back with dusky margins, fins all dusted; no defined humeral 
spot; a narrow dark lateral stripe widening above the middle of the anal, cover- 
ing over half the caudal peduncle, contracted again on middle caudal rays. 
18. HyYPHESSOBRYCON ROBUSTULUS (Cope). 
Hemigrammus robustulus Corr, Proc. Amer. philos. Soc., 1870, 11, p. 561 (Pebas); 1878, 17, p. 690 
(Peruvian Amazon); Fowuer, Proc. Acad. nat. sci. Phil., 1906, p. 335, fig. 24 (Pebas; Peruvian 
Amazon). 
Tetragonopterus robustulus EIGENMANN & EIGENMANN, Proc. U.S. N. M., 1891, 14, p. 54; Urey, Ann. 
N. Y. acad. sci., 1895, 8, p. 286. 
Hyphessobrycon robustulus EIGENMANN, Rept. Princeton univ. exped. Patagonia, 1910, 3, p. 437. 
Hasitrar.— Upper Amazon. 
One Cotype 8083 Acad. nat. sci. Phil. 44 mm. Pebas 
Head 3.4-3.5; depth 2-2.25; D. 11; A. 27; scales 7-35-6; eye 3 in the 
head; interorbital just equal to the eye. 
Compressed; deepest at the vertical from the origin of the dorsal; depth 
of head at the base of the occipital process 1.5 in the greatest depth. Preventral 
region rather narrow, without complete series of median scales. 
Occipital process 4.25 in the distance from its base to the dorsal, bordered 
by 2 scales. Interorbital region very slightly convex. Frontal fontanel trian- 
gular, one half of the parietal without the occipital groove. Second suborbital 
leaving a narrow naked margin behind and below. Snout short, mouth large. 
