ElGENMANN : THE EXPEDITION TO BRITISH GUIANA. 29 



Occipital process one fourth or one-fifth of the distance from its 

 base to the dorsal, bordered by four scales on the sides; interorbital 

 flat, the upper margin of large eye on a level with the middle of inter- 

 orbital ; frontal fontanel as long as the parietal, narrower than the 

 parietal, reaching to above the anterior margin of the pupil ; second 

 suborbital corrugate, leaving a wide naked margin ; premaxillary max- 

 illary border without a distinct angle, moderately oblique ; maxillary of 

 nearly equal width throughout, not slipping under or over the first 

 suborbital ; snout blunt, the lower included. 



Mandible with four to six narrow graduate teeth, with a large central 

 and a minute lateral cusp on each side ; sides of mandible with about 

 ten minute teeth ; premaxillary with four to seven teeth in a line 

 parallel with the second row, which consists of about five v to seven 

 three-lobed and one to three conical teeth ; maxillary with eleven to 

 sixteen conical or three-lobed teeth along about half the length of the 

 maxillary. 



Gillrakers 44-9. 



Scales everywhere regularly imbricate, without interpolate scales . 

 each scale with several radiating striae ; lateral line slightly decurved ; 

 anal sheath of a single series of graduate scales along the base of the 

 first rays ; caudal naked ; axillary scale small. 



Origin of the dorsal a little in advance of the middle, pointed, the 

 rays very rapidly decreasing from the highest, which is equal to about 

 a third of the length. 



Anal at origin and the third dorsal ray about equidistant from the 

 snout, emarginate ; ventrals extending slightly beyond origin of anal ; 

 pectorals beyond base of ventrals. 



Straw-colored, a silvery lateral band, slightly iridescent. A large 

 conspicuous, sub-circular spot over the sixth to eighth scale of the 

 lateral line occupying the width of two scales (this spot frequently 

 with a lunate encroachment in front); upper part of opercle and area 

 below eye spotted, sometimes the rest of the cheek also spotted ; a 

 black median line more or less evident ; a large caudal spot extending 

 to near the middle (sometimes further) of the median caudal rays ; 

 scales of the back always broadly margined with black, those of the 

 flanks less so ; above the anal the markings of the margin of the scales 

 mixed with the lines of chromatophores following the muscle segments ; 

 tips of caudal nigrescent; anal nearly uniformly dotted, or the base 

 and tip dotted, the rest hyaline ; first anal rays milk-white. 



