372 MEMOIRS OF THE CARNEGIE MUSEUM 



I have examined the types of B. falcatus and B. schomburgkii in Berlin. The 

 latter is undoubtedly the young of the former. It agrees with it in the markings 

 of both the fins and in the lateral bands, which follow the middle of the rows of 

 scales. 



227. Brycon siebenthalae sp. nov. (Plate LIV, fig. 3.) 



One specimen, 204 mm. Mud Creek, Aruka River. (C. M. Cat. No. 1819.) 



Head 4; depth 3; D. 11 ; A. 26; scales 12-64-7. Eye 1 in snout, 3.75 in head, 

 2 in interorbital. 



Compressed; head short, blunt, broad; ventral profile regularly and more 

 greatly arched than the dorsal; preventral area rounded, predorsal region bluntly 

 keeled. 



Interorbital arched; second suborbital leaving a narrow naked margin; upper 

 jaw scarcely projecting; twelve teeth in the outer series of the upper jaw; four 

 large teeth in the outer row of the lower jaw. 



Origin of dorsal midway between tip of snout and base of middle caudal rays, 

 the third ray longest, equal to head without opercle; caudal broad, emarginate, the 

 lobes rounded, 4.5 in the length; pectorals not reaching ventrals. 



A faint humeral spot; series of dark lines between the rows of scales, most 

 conspicuous over the anal. 



Pectorals and ventrals blue-black, the remaining fins dark. 



I take pleasure in naming this species for Miss Maud Siebenthal, who has pre- 

 pared many of the illustrations for this volume. 



Chalceus Cuvier. 

 Chalceus Cuvier, Mem. Mus. d'Hist. Nat., IV, 454. 



Type, Chalceus macrolepidotus Cuvier. 



With the dentition of Brecon, but an outer series of multicuspid and an inner 

 series of conical teeth in the lower jaw; three series of teeth in the premaxillary. 

 Scales of the back and down to the lateral line very large; lateral line much decurved, 

 the scales below it much smaller than those above it. Gill-membranes free; belly 

 rounded. 



A single species is known. 



228. Chalceus macrolepidotus Cuvier. 



Chalceus macrolepidotus Cuvier, Mem. Mus. d'Hist. Nat., IV, 454, pi. 21, fig. 1 — 

 Cuvier and Valenciennes, Hist. Nat. Poiss., XXII, 1848, 240. — Schom- 

 burgk, Fishes Brit. Guiana, I, 1841, 216, pi". 14 (Essequibo). — Gunther, 



