EIGENMANN: THE FRESHWATER FISHES OF BRITISH GUIANA 383 



Scales a little less regular than in gymnogenys. 



Sides more or less obscurely spotted; humeral spot obscure or none; vertical 

 fins nearly black; a lunate light spot, largest in the young, in the center of the 

 caudal. 



236. Serrasalmo stagnatilis Schomburgk. 



" Arri' ' (of the Macusi Indians). 

 Serrasalmo stagnatilis Schomburgk, Fishes Brit. Guiana, I, 1841, 222. (D. 17; 

 A. 32; P. 15.) 

 I am not able to place this species. 



Pygocentrus Miiller and Troschel. 



Pygocentrus Muller and Troschel, Horse Ichth., I, 1845, 20. 



Type, Serrasalmo piraya Cuvier. 



Belly trenchant, serrate; premaxillary with a single series of teeth; no teeth 

 on the palate; teeth in the jaws trenchant; those of the upper jaw with a notch on 

 the lateral edge; anal partly scaled. 



Key to the Guiana Species of Pygocentrus. 



a. Abdominal serra 40; depth 1.7-2; D. 18; A. 33-35; lateral line 105; interorbital a little less than half the 



length of the head; second suborbital in contact with the preopercle niger. 



aa. Abdominal serra? less than 35. 



b. Depth about 2 in the length; head heavy, about 3 in the length. D. 17-18; A. 30-33; lateral line 95- 

 100; abdominal serra 24-27; snout short, 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; anal slightly falcate; 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 1.6-1.75; head 3.12-3.5; D. 15 or 16; A. 32-34; lateral line 90; abdominal serra 27-33; snout 

 short, blunt, 4.33 in the head; eye 3.5-4; interorbital 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. Gill-rakers minute, about fifteen 

 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 scapularis. 



bbb. Depth 1.42; head 3.33; D. 15 or 16; A. 30-33; abdominal serra 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 in the angle of the preopercle, nearly half as high as the second suborbital; origin of dorsal 

 but little nearer to base of caudal than to tip of snout ; about eight 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 base of anal and the anal margin black; base of anal white; 

 dorsal and adipose blackish bilineatus. 



