262 PROCEEDINGS OF THE ACADEMY OF [Apr., 



teriorly at base of occipital process. Opercle widely and unevenly 

 triangular. Occipital process extends back toward dorsal as narrow 

 slender prolongation f of space. 



Gill-opening extends forward nearly opposite front eye margin. 

 Gill-rakers 4+6, slender, lanceolate, firm, about f of filaments. 

 Latter 2| in eye. Isthmus broadly convex. 



Body covered with smooth skin, and no rugose bony surfaces. 

 L. 1. complete, midway along side, and extends to median caudal 

 base. 



Dorsal origin nearer adipose fin origin than snout tip, slender 

 pungent spine smooth-edged and equals about half length of fin, 

 ending in long slender flexible tip. Second dorsal ray longest and 

 extends back as far as any of others. Adipose fin inserted nearly 

 midway between front eye edge and caudal base, fin low, graduated 

 up at first, and its length 2f in combined head and trunk length. 

 Anal inserted nearly midway between ventral origin and hind basal 

 edge of adipose fin, first to fourth branched rays subequally longest 

 and fin rounded. Caudal very long, deeply forked, lobes slender, 

 pointed, and upper longer. Pectoral low, spine pungent, outer 

 distal edge and median posterior edge with small antrorse serrse, 

 depressed fin extending 1| to ventral. Latter inserted about oppo- 

 site fifth dorsal ray base, fin reaching If to anal. Vent close behind 

 ventral bases, or about first fifth in space between ventral and anal 

 origins. 



Color in alcohol pale or very light brownish generally on upper 

 surfaces, lower surface paler or translucent whitish. Upper surface 

 of darker tint, due to minute dusky dots. A dark streak, made 

 up of closely set dusky dots, extends from snout tip to caudal base, 

 embracing. 1. 1. Lips pale brownish. Maxillary barbel brownish, 

 and other barbels whitish. Dorsal largely pale or translucent 

 basally on membranes, upper or distal halves dusky. Adipose fin 

 and caudal dusky-gray. Other fins pale or grayish. Iris slaty. 

 Length 80 mm. 



Type, No. 39,340, A. N. S. P. Rupununi River, British Guiana. 

 J. Ogilvie. 



Also, paratype, No. 39,341, A. N. S. P., same data. Head 4f ; 

 depth 7; D. I, 6; A. vi, 8, i; snout 2| in head; eye 31; maxillary 

 3f ; mouth width 3; interorbital 4; length 81 mm. 



This species differs from Rhamdella foina (Miiller and Troschel)^* 



1* Pimelodus foina Miiller and Troschel, Reis. Schomhurgk, III, 1848, p. 628. 

 Takutu. 



