eigenmann: tetragonopterid characins. 105 



Third anal ray of $ (i. e., the first fully-developed ray) provided with a large 

 retrorse hook on each side. 



A faint, ill-defined, silvery lateral band with a gray line above it. Middle 

 caudal rays jet black, the color spreading over base of fin. Scales and fins 

 minutely punctate. Sides brassy, iridescent. No humeral spot. 



One specimen, 50 mm. long. Lake Hyanuary. 



Bryconamericus heteresthes, sp. nov. 



The most slender species of the genus. 



Head 4-J-; depth 3.75-4.25 ; D. 10 (everything counted) ; A. usually 19. 



Slender, very little compressed, the width about one-half the depth. 



Occipital process very short, about 8 in the space from its base to the dorsal, 

 bordered by two scales. 



Four or five, rarely six, teeth in the front row of the premaxillary, the second 

 withdrawn from the line of the others. 



Scales deeply imbricate, without striae. 



Highly iridescent silvery; a silvery lateral band, two-thirds as wide as eye, from 

 humeral spot to caudal ; a vertical humeral spot ; a few pigment cells on upper 

 part of opercle and preopercle. Fins hyaline, without chromatophores. Anterior 

 anal rays of males witli numerous recurved hooklets. 



Many specimens, 27-49 mm. long. Tapajos. 



Bryconamericus stramineus, sp. no v. 



Head 4.5-4.75 ; depth 4.25-4.5 ; D. 10 ; A. about 22. 



Extremely slender, elongate, the ventral profile slightly more arched than the 

 dorsal. 



Occipital process very short, about 8 in the space from its base to the dorsal. 



Scales cycloid, everywhere regularly imbricate. 



Straw colored in alcohol ; a conspicuous silvery band ; a very faint humeral 

 spot ; middle caudal rays with faint dots. 



Three specimens, 44 to 49.5 mm. Piracicaba and Uruguay River. 



Bryconamericus boops, sp. nov. 



Head 4 ; depth 3.6 ; D. 10 ; A. 22. 



Elongate, sciaenoid. Gill-rakers very short, about 8+12. 



Frosted silvery. A humeral spot above the fourth and fifth scales of the lateral 

 line ; a plumbeous lateral band becoming darker on the caudal peduncle ; middle 

 caudal rays dusky ; dorsal dusky except tips of first two rays. 



One specimen, about 76 mm. in total length (60 mm. to base of C.). Maldonado. 



Bryconamericus breviceps, sp. nov. 



Distinguished by the short head and the small fins. 



Head 4.5-4.66 ; depth $ and spent 9 about 3 ; 9 with eggs 2.66-2.8 ; D. 

 10-11 : A. 20-23. 



