114 THE AMERICAN CHARACIDAE. 
4. Knopus, gen. nov. 
xvd, a trifle, d50us, tooth. 
Typr.— Bryconamericus breviceps Eigenmann. 
This genus differs from Moenkhausia as Bryconamericus differs from 
Astyanax. 
Second suborbital expanded, in contact with the preopercle below; four 
teeth in the second row of the premaxillary; caudal scaled at its base; lateral 
line but little decurved. 
Haxpitrat.— Tapajos, Tocantins, and Paraguay Rivers; Merida, Venezuela. 
Key to the Species. 
a. Depth 3.5-4.24. 
b. Dentary with a series of four large teeth, the series continued on the side by graduate teeth. 
Head 4.25; depth 3.75-4.25; eye 2.75 in head, equals interorbital; maxillary with 2 or 3 
teeth; D. 10; A. 18-21, usually 19; scales 5-35 to 38-3; caudal entirely hyaline. 
1. heteresthes (Kigenmann). 
bb. Dentary with eight graduate teeth. Head 4; depth 4; eye 3.25 in head; 1.25 in interorbital; 
maxillary with 3 teeth; D. 10; A. 16; scales 14-33-2.............. 2. meridae Kigenmann. 
bb. Dentary with 3 or 3.5 large teeth followed by abruptly smaller teeth on the side; head 4; depth 
3.5-3.75; eye 2.5-2.66, equals the interorbital; maxillary with 1-5 (usually 3) teeth; D. 10, 
A. 22-24; scales 5-39-3.5 or 4; middle caudal rays dark. 
3. moenkhausii (Eigenmann & Kennedy). 
aa. Depth 3 or less than 3 in the length; dentary with four large graduated teeth and a few smaller, 
similar ones on the side. 
c. Head 4.5-4.66; depth 2.66-3; D. 10 or 11; A. 20-23; scales 5.5 or 6-38 to 41-4; eye 
3-3.5; maxillary teeth 2 or 3. Caudal with numerous small scales. 
4. breviceps (Higenmann). 
ce. Head 4.25; depth3 +; D.10; A. 20; scales 4.5-36-3.5, eye 3; interorbital 2.8; maxil- 
lary with three broad teeth; caudal with large scales on the basal third. 
5. victoriae (Steindachner). 
ccc. Head 3.75; depth 3; D. 10; A. 20; scales 642-4.5; eye 3; maxillary with three teeth. 
6. chapadae (Fowler). 
cece. Head 3.5; depth 3; D. 10; A. 27; scales 5-38-4; interorbital 2.2 in the head; maxil- 
lary. without tooth is.)0s kisi. s cess ees ea eke reise si aeremyene 7. jacunda (Fowler). 
ececc. Head 4; depth 2}; D.9; A. 28; scales 6-39-4; interorbital 2.4 in the head; maxillary 
without, teeths a. o > sects ot unrcematety cote cael ae cerns 8. smithi (Fowler). 
1. Knopus HETERESTHES (EHigenmann). 
Plate 10, fig. 4. 
Bryconamericus heteresthes EIGENMANN, Bull. M. C. Z., 1908, 52, p. 105 (Tapajos); Rept. Princeton 
univ. exped. Patagonia, 1910, 3, p. 434. 
Hapitat.— Tapajos. 
Forty specimens, 20862 Cotypes 27-51 mm. Tapajos Dexter, James, Talisman 
