ElGENMANN : THE EXPEDITION TO BRITISH GuiANA. 47 



widest, the superior bar brown, shading into black at both ends. Anal 

 hyaline, a black bar across tips of the last rays. 



Subfamily SERRASALMINiE. 



Genus Pygocentrus Miiller & Troschel. 

 Pygocentrus bilineatus sp. no v. 



Type, 102 mm. (No. 1072 Carnegie Museum Catalog of Fishes.) 

 Aruka River. 



Cotypes, 95 and no mm. Aruka River. (C. M. Cat. No. 1073; 

 I. U. Cat. No. 11756.) 



Cotypes, 2 specimens, 43 and 56 " mm. Creek in Moro Passage. 

 (C. M. Cat. No. 1074; I. U. Cat. No. 11757.) 



This species can best be described by means of a " Key " to the 



species so far recorded in British Guiana. 



a. Abdominal serrae 40; depth if; D. 18; A. 33-35; lat. 1. 105; interorbital a 

 little less than half the length of the head ; second suborbital in contact with 

 the preopercle. niger. 



an. Abdominal serrae less than 35. 



b. Depth about 2 in the length ; head heavy, about 3 in the length ; D. 17-18 ; 

 A. 30-33; lat. 1. 95-100; snout short; abdominal serrae 24, very blunt ; 

 interorbital nearly half the length of the head ; a very narrow naked area 

 on the cheek ; origin of dorsal nearly equidistant from base of middle caudal 

 rays and front of eye ; sides profusely spotted ; a V-shaped black bar on 

 the base of the caudal ; margin of caudal dark ; adipose fin rayed in the 

 adult. piraya. 



bb. Depth 1.5— 1.75 ; head 3.12-3.5; D. 15 or 16; A. 32-34; lat. 1. 90; ab- 

 dominal serrae 27-33 ; snout short, blunt, 4.33 in the head ; eye 3.5-4; in- 

 terorbital 2.33 ; a narrow lens-shaped naked area on the cheek, not more 

 than one-fourth as wide as the second interorbital ; origin of dorsal about 

 equidistant from base of middle caudal rays and front of eye. Gillrakers 

 minute, about 15 on the lower limb ; a large diffuse humeral blotch ; sides 

 with numerous small spots ; caudal in the adult with a narrow hyaline 

 margin, the rest of the fin black ; in the young hyaline, with a faint basal 

 V-shaped bar. scaptilaris. 



bbb. Depth if; head 3.33; D. 15 or 16; A. 30-33; abdominal serrae 30 or 

 31 ; lateral line 73-76 ; snout pointed, equal to the eye, 3.5 in the head ; 

 interorbital 2.5 in the head ; a lens-shaped naked area on the angle of the 

 preopercle nearly half as high as the second suborbital ; origin of dorsal 

 but little nearer base of caudal than tip of snout ; about 8 minute gill- 

 rakers on the lower arch ; a prominent humeral spot ; sides obscurely 

 spotted, margin of caudal and a V-shaped basal band black ; scales along 



17 This specimen seems to have teeth on the palate, depth 1.75 ; D. 15 ; A. 33 ; 

 serrae 30. 



