196 PROCEEDINGS OF THE NATIONAL MUSEUM vol.94 



straight line; anterior nostrils tubular, forward of base of maxillary- 

 barbel; anterior and posterior barbels widely separated; supraoccipital 

 process covered with skin and not meeting the predorsal plate; 

 gill rakers about 4+8 to 10; caudal lobes roimded, upper lobe 

 with 7 branched rays and lower with 9; caudal peduncle com- 

 pressed. No teeth on vomer or palatines; posterior margins of 

 dorsal, anal, pectoral, and pelvic fins rounded; lower lobe of caudal 

 fin rounded, broader than upper lobe; upper and lower lobes separated 

 by a deep incision of the membrane between the two shortest mid- 

 caudal fin rays; adipose fin very long, its origin about an eye diameter 

 behind base of dorsal fin ; maxillary barbel flatfish, reaching to caudal 

 peduncle or a little shorter, outer mental barbel extends to tips of 

 pectorals or to base of pelvics; inner mental barbel reaching to base 

 of pectorals or one-thu"d out their length; pelvic fins reach two-thirds 

 the way to origin of anal fin, and pectorals two-thirds the way to 

 the insertion of the pelvic fins; the free margin of the eye becomes less 

 free ventrally on the small specimens and on those as short as 20.5 

 and 26 mm. the margin of the eye is not free (it is thought that the 

 identification of the two small specimens is correct); the top of the 

 head is covered with rather thick skin, so that the posterior end of the 

 supraoccipital process is obscured, but it does not meet the embedded 

 predorsal plate; fontanel in middorsal line between the orbits small, 

 closed or nearly closed in adults. 



Color. — The general color is blackish above, paler below, with the 

 belly and underside of head nearly white ; a blackish blotch occurs over 

 the tympanic area of air bladder just behind head and forms a faint 

 darkish band just in front of dorsal fin base, most distinct on the half 

 grown and young; all fins grayish to blackish; in the young the 

 lateral line is blackish; posteriorly the interradial membrane of the 

 dorsal fin is blackish along its middle third with a hyaline area an- 

 teriorly, less distinct in the larger specimens; peritoneum pale. 



RHAMDIA HUMIUS (GUnther) 



Pimelodus humilis Gunther, Catalogue of the fishes in the British Museum, vol. 



5, p. 129, 1864 (Venezuela). 

 Rhamdia humilis Eigenmann and Eigenmann, Occ. Pap. California Acad. Sci., 



vol. 1, p. 126, 1890 (Venezuela), — Eigenmann and Allen, Fishes of western 



South America, p. 94, 1942 (Venezuela). 



RHAMDIA GUAIRENSIS Eigenmanii 



Rhamdia guairensis Eigenmann, Indiana Univ. Studies, vol. 7, No. 44, p. 6, 1920 

 (Rfo Guaire near Caracas, Venezuela). 



RHAMDIA QUELEN (Quoy and Gaimard) 



Pimelodus quelen Quoy and Gaimard, Voyage autour du monde . . . Uranie, 

 Zool., pi. 49, figs. 3-4, 1824. 



Rhamdia quelen Eigenmann, Indiana Univ. Studies, vol. 7, No. 44, p. 6, 1920 

 (Rio Castano and Rfo Bue, Maracay; El Concejo, Rio Tiquirito). — Pearse, 

 Univ. Wisconsin Studies, No. 1, pp. 23, 45, 1920 (Rio Castafio, Venezuela). 



