eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 205 



Distance from snout to dorsal 3.6 in the length; the spine slender, with minute 

 wide-set teeth on the anterior margin, more numerous minute teeth on the posterior 

 margin; pectoral spine slender, pungent, slightly rough in front, with small curved 

 teeth along its entire inner margin; caudal deeply forked, the middle rays not half 

 as long as the outer rays, which are 4.5 in the length; origin of the anal a little 

 nearer to the base of the middle caudal rays than to the rictus; ventrals reaching 

 beyond origin of anal; pectorals four-fifths the distance to the ventrals. 



Dark chocolate above, shading to the anal; ventral surface light; back ob- 

 scurely marbled; dorsal, base and tips of caudal, upper surface of pectoral and 

 ventral, except their last rays, dark. 



This species is near dentatus Kner and ucayalensis Castelnau, but differs in 

 the width of the head, the length of the snout, the mouth, color, etc. 



76. Ageneiosus brevifilis Cuvier and Valenciennes. 



Ageneiosus inermis (not Silurus inermis Linnaeus or Bloch) Cuvier and 

 Valenciennes, Hist. Nat. Poiss., XV, 1840, 240, pi. 440 (Surinam) .- 

 Castelnau, Anim. Am. Sud, Poiss., 1855, 48 (Amazon). 



Ageneiosus brevifilis Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 242 

 (Cayenne).— Kner, SB. Akad. Wiss. Wien, XXVI, 1857, 438 (Rio Oujaba).- 

 Gunther, Catalogue, V, 1864, 192 (River Capin, Para); Proc. Zool. Soc. 

 London, 1868, 229 (Xeberos).— Cope, Proc. Am. Philos. Soc, XVII, 1878, 

 676 (Peruvian Amazon). — Eigenmann and Eigenmann, Proc. Cal. Acad. 

 Sci., (2), I, 1888, 150 (name only); Occasional Papers Cal. Acad. Sci., I, 

 1890, 309. — Eigenmann, Repts. Princeton Univ. Exp. Patagonia, III, 1910, 

 397. 



Pseudageneiosus brevifilis Bleeker, " Silures de Suriname," 1864, 83, pi. 16, fig. 1 

 (Surinam) . 



Hypophthalmus dawalla Schomburgk, Fishes Brit. Guiana, I, 1841, 191, pi. 9 

 (Guiana). — Muller and Troschel, in Schomburgk, Reisen, III, 1848, 643. 



Ageneiosus dawalla Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), I, 

 1888, 150 (name only); Occasional Papers Cal. Acad. Sci., I, 1890, 309. 



Ageniosus sebw Gunther, Catalogue, V, 1864, 192 (copied). 



One specimen, a male, 445 mm. Lama Stop-Off. (C. M. Cat. No. 1711a.) 

 Head 3.66; depth 5; D. 1,6; A. 34; V. 8; P. 1,14; Br. 9; eye 3.5 in snout, 



6.5 in head, 5.5 in space between the eyes below. 



Profile steep, concave; head depressed, broad; fontanel reaching eye, the 



groove beyond the posterior margin of the eye; maxillary barbel osseous to near its 



