270 MEMOIRS OF THE CARNEGIE MUSEUM 



Subfamily Prochilodusle. 

 Prochilodus Agassiz. 

 Prochilodus Agassiz, Selecta Gen. et Spec. Pise. Bras., 1829, 62. 

 Pacu Spix, Selecta Gen. et Spec. Pise. Bras., 1829, pis. 38, 39. 

 Chilomyzon Fowler, Proc. Acad. Nat. Sci. Phila., 1906, 309, fig. 11 (steindachneri) . 



Type, Prochilodus argenteus Agassiz. 



Fishes of moderate or large size. Mouth broad, jaws very weak; teeth in- 

 serted on lips, movable, in a single series on the sides, in two series in the middle. 

 A procumbent dorsal spine; scales rough ctenoid; mouth convertible into a large 

 circular sucking disk, not strictly protractile. 



A genus of about twenty-five known species, from the La Plata to Peru, the 

 Rio Magdalena, and western Ecuador. One species occurs in the Essequibo, 

 and another, closely allied, across the divide, in the upper branches of the Ireng. 



127. Prochilodus rubrotaeniatus Schomburgk. 



Prochilodus rubrotaeniatus Schomburgk, Fishes Brit. Guiana, I, 1841, 258, pi. 28 



(Rios Branco, Negro and Essequibo). — Schomburgk, Reisen, III, 1848, 644 



(Essequibo). — Steindachner, "Fisch-faunadesCauca," etc., 1880, 16 (Cauca). 



— Eigenmann and Eigenmann, Proc. U. S. Nat. Mus.,XIV, 1891,48. — Eigen- 



mann, Repts. Princeton Univ. Exp. Patagonia, III, 1910, 424. 



Prochilodus nigricans Gunther (not of Agassiz), Catalogue, V, 1864, 295 (Esse- 

 quibo). 



One specimen, 303 mm. Tumatumari. (C. M. Cat. No. 2064.) 

 Seven specimens, 230-330 mm. Rockstone sand-bank. (C. M. Cat. No. 



2065a-d; I. U. Cat. No. 12254.) 



Head 3.75-3.8; depth 2.45-2.6; D. 12 (counting the last filament); A. usually 



10, sometimes 11, or even 12; scales 7 or 8-45 or 46-6 or 7; eye 1.33-1.5 in snout, 



3.75-4 in head, 2.4 in interorbital. 



Heavy, compressed, deep, subrhomboidal; anterior profile steep, rounded to 



the nape, concave over the eyes; predorsal area bluntly keeled, with a median 



series of about fourteen scales; preventral region broad, angulated at the sides, 



with a median series of slightly keeled scales; postventral region narrowly keeled. 



Head very broad, convex between the eyes; mouth terminal, the lower jaw but very 



slightly shorter than the upper. 



Scales large, rough, denticulate at the margin, very regularly arranged; fins 



naked; a large axillary scale; lateral line straight. 



Fins large; dorsal rounded, sometimes high, the middle ray in No. 2064 being 



