EIGENMANN: the freshwater fishes op BRITISH GUIANA 381 



Serrasalmo gymnogenys Gunther, Catalogue, V, 1864, 371 (River Capin; British 

 Guiana). — Eigenmann and Eigenmann, Proc. U. S. Nat. Mus., XIV, 1891, 

 60.— Ulrey, Ann. N. Y. Acad. Sci., VII, 1895, 298 (Marajo).— ? Perugia, 

 Ann. Mus. Geneva, (2a), X, 1891,650 (Resistencia, Chaco Centrale). — Pelle- 

 grin, Bull. Mus. d'Hist. Nat., V, 1899, 157 (Apure).— Eigenmann, Repts. 

 Princeton Univ. Exp. Patagonia, III, 1910, 442. 



Twenty-six specimens, 31-144 mm. Rockstone. (C. M. Cat. Nos. 1108a-c 

 and 1122a-d; I. U. Cat. No. 11646.) 



One specimen, 57 mm. Wismar. (C. M. Cat. No. 1111.) 

 One specimen, 47 mm. Tumatumari. (C. M. Cat. No. 1112a.) 

 Two specimens, 37-125 mm. Crab Falls. (C. M. Cat. No. 1130a; I. U. Cat. 

 No. 11647.) 



Four specimens, 104-141 mm. Below Packeoo. (C. M. Cat. No. 1133a; 

 I. U. Cat. No. 11645a-6.) 



Head 3.1-3.25; depth 1.6-1.7; D. 15 or 16; A. 32-37; ventral serrse 22-33, of 

 which one is bifid before the anus and one grooved with two antrorse and two 

 retrorse spines behind the anus; lateral line 77-80; eye 3.25 in the head, 1.3 in the 

 interorbital, .6 in the snout. 



Deep; snout obliquely truncate, the chin projecting; second suborbital leaving 

 from one-third to two-sevenths of the check naked; opercles and suborbitals pro- 

 fusely striate; gill-rakers minute, about 10 -F 10; teeth oblique, usually with a 

 notch on one side, sometimes on both sides on those of the premaxillary; pre- 

 maxillary with seven teeth, of which the third is very much smaller than the rest; 

 lower jaw with seven slightly graduated teeth. 



Dorsal short, rounded, its base a little longer than its distance from the adipose; 

 adipose short; caudal lunate; anal with a slight lobe in front; ventrals reaching to 

 the anal groove or a little shorter; pectorals to, or a httle past, the vertical from the 

 origin of the ventrals. 



First few scales of the lateral line larger than the neighboring scales, becoming 

 smaller on the sides than those above or below the line, but of the same number as 

 there are transverse series; scales regularly imbricate. 



A large diffuse humeral spot; sides variously spotted; caudal with a basal 

 V-shaped black band, increasing in width with ag'e; opercles rosy in life, the color 

 most intense on the lower corner of the opercle, the red sometimes extending over 

 the lower part of the sides and breast; anal tinged with orange in front. 



I have examined one of the specimens mentioned as aureus by M tiller and 

 Troschel. It agrees with specimens taken by me in all but the color of the caudal, 



