ElGENMANN I THE EXPEDITION TO BRITISH GUIANA. 15 



ray 2^ as long as the penultimate, 3J/3 in the length; caudal lobes 

 equal, a little longer than the longest dorsal ray ; anal emarginate, its 

 longest ray when depressed reaching the base of the last but fourth 

 anal ray ; ventrals reaching anal, pectorals about one scale beyond 

 origin of ventrals. 



No caudal spot, a large horizontally oval humeral spot continued 

 below to the origin of the pectoral ; a dark band from origin of dorsal 

 obliquely downward and forward to the lateral line ; a dark median 

 lateral line ; white below, dark along back ; each scale of the side 

 with a conspicuous dark crescent along its middle. 



In life all fins but the adipose strongly tinged with red ; middle of 

 adipose yellow. 



This species, abundant in the Potaro River above and below the 

 Kaieteur, is dedicated to the memory of C. Barrington Brown, the dis- 

 coverer of this most beautiful fall. 



Moenkhausia shideleri sp. nov. 



Type, 65 mm. (No. 1012 Carnegie Museum Catalog of Fishes.) 

 Bartica. 



Cotype, 73 mm. Bartica. (I. U. Cat. No. 11716.) 



Cotype, 63 mm. Tumatumari. 



This species has the largest eye of any in the genus. 



Head 3.7-3.8; depth 2.5-2.7; D. 10; A. 26; scales 5-34-3 or 

 4; eye 2.1 ; interorbital 2.4 or 2.5. 



Elongate, subrhomboidal, the ventral surface in front of the anal 

 distinctly arched ; a very slight depression over the eye ; preventral 

 area rounded, a series of median scales ; post-ventral region narrowly 

 rounded, with a median series of large scales, bordered by slightly 

 asymmetrical scales. Predorsal area keeled to near the occipital crest. 

 A median series of scales between the dorsal and occipital crest, the 

 length of which is about one-fifth of the distance from its base to the 

 dorsal. 



Interorbital slightly convex ; second suborbital leaving a narrow 

 naked border on the cheek. Maxillary 3 in the head ; four or five 

 teeth in the front row of the premaxillary, the third somewhat removed 

 from the rest ; five graduated teeth on the inner row ; two small teeth 

 on the maxillary ; mandible with four large teeth and numerous small 

 ones on the side. 



Gill rakers about 9 + I2 - 



