260 ■* PROCEEDINGS OF THE ACADEMY OF [Apr., 



tip and caudal base, spine with front edge distally furnished with a 

 series of antrorse serrse under skin, and tip ends in flexible ray-like 

 end. First branched dorsal ray longest, depressed tip falls slightly 

 short of tips of last. Origin of adipose fin slightly nearer gill-opening 

 than caudal base, slopes up gradually at first until near middle when 

 uniformly high, and its entire length about Sg- in combined length 

 of head and trunk. Caudal moderate, well forked, lobes about 

 equal, sharply and similarly pointed, and rudimentary rays well 

 developed. Anal inserted slightly nearer ventral origin than caudal 

 base, and third branched ray about longest, edge of fin rounded. 

 Pectoral low, with strong spine, both edges with antrorse serrse 

 though inner distal edge smooth, and depressed fin reaches 1^ to 

 ventral. Ventral inserted just behind dorsal base, fin rounded, and 

 extends about f to anal origin. Vent anterior, falls about first f 

 in space between ventral and anal origins. 



Color in alcohol dull or pale uniform bro^vnish above, becoming 

 somewhat mottled or variegated with darker brownish on caudal 

 peduncle, posterior region of trunk and caudal base. Lower surface 

 of body pale brownish to whitish. Iris slaty. Lips pale. Max- 

 illary barbels brownish, and mental barbels pale or whitish like chin. 

 Fins all grayish-brown, tinted a little deeper medianly. 



Length 145 mm. 



Type, No. 39,339, A. N. S. P. Rupununi River, British Guiana 

 J. Ogilvie. 



Related to Rhamdia holomelas (Giinther),!^ and it may possibly 

 prove to be identical. However, Giinther gives the long adipose 

 fin as 2 to 2j in total length without caudal, maxillary barbels reaching 

 origin or middle of adipose fin, outer mental barbels reach middle of 

 pectoral, depth 5 to 5|, head 4, eye 2 in interorbital, caudal cleft 

 to base and color uniform black with brownish shade, lighter on 

 belly. His examples were a foot long, though he also had young. 

 The inference would be that these characters would apply to young 

 and adult as their latitude allows. For this reason, as mj^ example 

 will be seen to differ considerably, especially in the above-mentioned 

 points, I allow it a^ distinct. 



(Named for the Rupununi River.) ;, 



Rhamdella leptosoma >^v- nov. Fig. 12. 



Head 4|; depth 8i; D. I, 6; A. vi, 8; P. I, 9; V. i, 5; head width 

 I5 in its length; head depth at occiput If; snout 3j; eye 3j; max- 



" Pimelodus holomelas Giinther, Cat. Fish. Brit. Mus., V, 1864, p. 120. 

 Essequibo. 



