eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 301 



in the adult; mouth terminal in the young, slightly oblique, becoming subterminal 

 or inferior with age. Four teeth on each side of each jaw. 



Origin of dorsal equidistant from snout and base of upper caudal lobe in the 

 young, farther forward in adult; margin of dorsal rounded, the highest ray about 

 5 in the length; upper caudal lobe but little longer than lower, 3.33-3.5 in the 

 length; anal emarginate, not reaching caudal ; ventrals reaching half-way to origin 

 or end of base of anal; pectorals a little more than half-way to middle of ventrals. 



A conspicuous, straight, dark chocolate band from upper part of gill-opening 

 to base of middle caudal rays, as deep as the eye or deeper; a narrower, similarly 

 colored band arched from the eye downward and back along the lower margin of 

 the caudal peduncle to the caudal ; a similar one curving upward slightly from above 

 the gill-opening to the adipose, bordered above by a faintly lighter area; the middle 

 of the back and base of last anal rays dark. A dark spot at base of pectorals. 



Tips of fins, bases of scales in the light areas of the sides, opercles, and cheeks 

 rosy or red in the adult. Light parts white to straw-color; gill-covers greenish 

 yellow; in the young the bases of all the fins are sometimes rusty. 



158. Leporinus nigrotseniatus (Schomburgk). (Plate XLII, figs. 1, 2.) 



Chalceus nigrotceniatus Schomburgk, Fishes Brit. Guiana, I, 1841, 213, pi. 13, fig. 

 2 (Rio Negro). 



Leporinus nigrotceniatus Muller and Troschel. Horse Ichth., I, 1845, 11, pi. 1, 

 fig. 7; in Schomburgk, Reisen, III, 1848, 634 (Pomeroon). — Cuvier and 

 Valenciennes, Hist. Nat. Poiss., XXII, 1848, 32 (Pedrero on the Rio Negro). 

 — Kner, "Familie der Characinen," i, 1859, 34 (Barra do Rio Negro; Rio 

 Branco).— Gunther, Catalogue, V, 1864, 309 (Essequibo). — Steindachner, 

 " Ichthyologische Beitrage," v, 1876, 62 (middle course of the Amazon).— 

 Eigenmann and Eigenmann, Proc. U. S. Nat. Mus., XIV, 1891, 51. — Eigen- 

 mann, Repts. Princeton Univ. Exp. Patagonia, III, 1910, 426. 



Leporinus margaritaceus u Gunther, Catalogue, V, 1864, 309 (Brit. Guiana). 



Six specimens, 120-207 mm. Tumatumari. (C. M. Cat. No. 1820«; I. U. 



Cat, No. 12112.) 



One specimen, 145 mm. Rockstone. (C. M. Cat. No. 1821.) 



31 Type, 177 mm. to the base of the middle caudal rays. British Museum. British Guiana, Schom- 

 burgk. 



Head 4.66; depth 5.16; D. 12; A. 10; scales 5.5-40-5. Eye 1.5 in snout, 3.8 in head, 1.6 in interorbital. 



Resembling nigrotwniatus in shape; dorsal 5 in the length, its origin equidistant from snout and adipose; 

 anal rounded, reaching the caudal. A silvery lateral band, each scale with a pearly base. No black spots or 

 other dark markings. 



Another specimen in the Berlin Museum, in which the lateral band is almost faded out, leaves no doubt 

 but that margaritaceus is simply a faded specimen of nigrotwniatus. 



