258 PROCEEDINGS OF THE ACADEMY OF [Apr., 



Color in alcohol dull brownish above or on back and upper surface 

 of head, lower or under surfaces and lips paler or whitish. From 

 dorsal origin down on back a pale streak, when below I. 1. it follows 

 latter below to caudal. Behind oblique lateral pale streak, another 

 lengthwise streak begins posterior to its crossing 1. 1. and continues 

 to caudal base, keeping parallel with 1. 1. its whole extent. On 

 caudal both pale streaks are merged in the median color of that 

 fin. Lower boundary of lower pale streak indicated by a pale grayish 

 lengthwise streak, made of minute dusky dots, which become closer 

 on caudal base and finally form a blackish streak across median 

 portion of lower caudal lobe nearly to its tip. In similar fashion 

 upper dark body color marks upper caudal lobe. Maxillary barbels 

 brownish above, pale or whitish below like mental barbels. Dorsal 

 fin whitish, with a large sharply contrasted superior median blackish 

 blotch. Adipose fin brownish. Remaining tints of caudal, on 

 regions not mentioned, whitish. Pectoral, ventral and anal whitish. 



Length 270 mm. 



Type, No. 39,338, A. N. S. P. Rupununi River, British Guiana. 

 J. Ogilvie. 



Known only from the above. It resembles Megalonema platy- 

 cephalum Eigemnann, but that species is said to be pale or nearly 

 uniform in color, with a pair of hidden spots at the caudal base and 

 the lower caudal lobe dusky. 



('Fa,3do<^, streak; (rriyim^ spot; with reference to the lengthwise 

 streaks and the dorsal blotch.) 



Chasmocranus longior Eigenmann. 

 One example, 87 mm. long. 



Rhamdia sebae (Valenciennes). 



One example, 127 mm. long. 



Rhamdia holomelas rupununi subsp. nov. Fig. 11. 



Head 3f ; depth 6|; D. I, 6; A, iv, 8; P. I, 8; V. i, 5; head width 

 \\ in its length; head depth at occiput IfV; snout 2f ; eye 4; max- 

 illary 4; mouth width 2|; interorbital 5; antero-internasal 5j; 

 dorsal spine 2; first branched dorsal ray If; second branched anal 

 ray 2\\ upper caudal lobe \\; least depth caudal peduncle 3; pec- 

 toral spine \\; pectoral fin 1|; ventral fin If. 



Body elongate, slender, moderately compressed, anteriorly slightly 

 depressed, deepest about dorsal origin, and edges all convexly 

 rounded. Caudal peduncle compressed, length about equals its 

 least depth. 



