Durbin : The Expedition to British Guiana. 59 



rounded, sometimes with complete series of nine or ten median 

 scales. 



Occipital process one-sixth of the distance from its base to the dorsal, 

 bordered by three scales, lnterorbital convex. Frontal fontanel 

 narrower than the parietals, triangular, and almost as long as the 

 parietals without the occipital groove. Second suborbital without 

 naked margins. Snout short, mouth moderately large, lower jaw in- 

 cluded only when the mouth is closed. Maxillary not quite equal to 

 the eye. Mandible a little longer than the eye, 2-2.4 in tne head. 

 Preopercle not deeply incised above. Premaxillary with four or five 

 four- or five-pointed teeth in the inner and three or four tricuspid 

 teeth in the outer row. Maxillary with two or four small conical or 

 three-pointed teeth. Dentary with a graduated series of four five- to 

 seven-pointed teeth, and several minute conical teeth on the sides. 



Gillrakers 10 + 6. 



Scales cycloid, regularly imbricate, no interpolated scales or rows of 

 scales, striae (about ten) variable in number, some scales of the pre- 

 dorsal region being probably lacking in some specimens. Caudal much 

 scaled. Anal sheath of about five scales covering the bases of the first 

 six to eight anal rays. Axillary scale developed. Lateral line with 

 pores on nine to twelve sometimes fifteen scales, lightly decurved. 



Origin of the dorsal equidistant from snout and caudal, penultimate 

 ray one-third of the longest, which is 3J into the length. Origin of 

 the anal on the vertical from the first or second scale behind the 

 dorsal. Anal deeply emarginate ; longest ray -§-- J of the length of 

 the base. Caudal half the length of the eye longer than the head, 

 much, scaled, ventral lobe slightly larger than the dorsal lobe. Ven- 

 trals on the vertical from the first scale in front of the dorsal, just 

 reaching the anal. Pectorals either not quite or just reaching the 

 ventrals 



No shoulder spot. A silvery lateral stripe extending from the 

 caudal to about the vertical from the first dorsal rays, and continued 

 forward by a few large scattered chromatophores. The black caudal 

 spot usually extending nearly or entirely to the end of the middle 

 caudal rays. Scales of the back and sides above the lateral stripe out- 

 lined with pigment, an olive stripe along the back, sides above stripe 

 straw-colored, scales below the stripe with a light blue iridescence. 

 All fins somewhat dusky. Males with a cherry-red spot on the base 

 of each caudal lobe, anterior anal margin with a white bar broadest 



