ElGENMANN : THE EXPEDITION TO BRITISH GUIANA. 23 



Cotypes, 2 specimens, 47-49 mm. Erukin, Lower Potaro River. 

 (C. M. Cat. No. 1041 ; I. U. Cat. No. n 734.) 



Evidently allied to bimaculatus and orthodus. It is readily distin- 

 guished from bimaculatus by its emarginate anal, the broad caudal band 

 and the absence of any stripe on the caudal peduncle. In the colora- 

 tion of the sides it approaches abramoides, the humeral spot being less 

 well denned, the black lateral line being absent. Its anal is distinctly 

 shorter than that of orthodus. 



Head 3.5 ; depth 2.6-3 J D. 1 1 ; A. 27 or 28, rarely 29; scales 8 

 (rarely 9) -37 to 38 7 -6 or 7 ; eye 2.75 ; interorbital 3. 7 



Elongate, subrhomboidal, profile rising rapidly in front, then curved 

 more gently to the dorsal ; ventral profile regularly rounded. Preven- 

 tral area convex, without a distinct median series of scales ; postventraj 

 area narrowly rounded ; predorsal area narrowly rounded, two scales 

 in front of the dorsal, the median line otherwise naked to the occipital 

 process. 



Occipital process very narrow, its width not quite half its length, 

 which is about \ as long as the distance from its base to the dorsal, 

 bordered by three scales on the sides. Interorbital smooth and con- 

 vex ; frontal fontanel a little narrower and a little shorter than the 

 parietal ; second suborbital leaving a considerable naked area which is 

 widest below ; mouth large, maxillary a little longer than the eye ; 

 normally four teeth in the outer series of the premaxillary, of which 

 the third is withdrawn from the line of the rest ; five teeth in the 

 second series ; maxillary with three small teeth ; mandible with four 

 large teeth in the dentary and abruptly minute ones on the side. 



Gill rakers 6 + 14, those of the upper arch excessively minute, 

 those of the lower arch about i the length of the eye. 



Scales of the sides regularly imbricate, no interpolated scales over 

 the anal ; scales of the ventral surface less regularly imbricate ; lateral 

 line but little decurved ; anal sheath composed of a single series of 

 scales along the base of the anterior rays. 



Ventrals but little nearer the snout than the dorsal, which is a little 

 nearer to the snout than to the caudal ; highest dorsal ray about 4 in 

 the length. Anal emarginate, the second and fourteenth rays reaching 

 the base of the twentieth ray. Ventrals not reaching anal, pectorals 

 just to ventrals. 



Coloration much as in abramoides, a dark bar crossing opercle, a 



7 In ten individuals five have 37, three have 38, one has 39, one 41 scales. 



