SOUTH AMERICAN NEMATOGNATHI. 151 



Avary; Villa Bella; Jutahy; Tapajos; Kio Mucuri; Tab- 

 atinga; Hyavary; Coary. The largest specimen exam- 

 ined is .34 m. long. 



Body much depressed towards the caudal, elongate. 

 Head conical, covered with thin skin, its greatest depth 

 1^ in its length; occipital crest narrow and long, reach-' 

 ing the comparatively large dorsal plate. A pore be- 

 tween the nasal openings, nearer the anterior. 



Maxillary barbels extend sometimes to the beginning 

 of the adipose, sometimes to near its tip; mental barbels 

 thin, the distance between them greater than their distance 

 from the postmental barbels, extending to the base of 

 the pectoral; postmentals to middle of pectoral. 



Eye large, If to 2J in snout, 4-5 in head, 1-1 J in 

 interorbital region, 1| to If diameters behind the rictus. 



Mouth small, its width 3 in the head; teeth of the 

 lower jaw in a shallow band which is interrupted in the 

 middle and tapers backwards beyond the angle of the 

 mouth. Teeth of the upper jaw in a narrow band, 

 not deeper than the deepest part of the mandibulary band, 

 sometimes interrupted in the middle. 



Gill-membranes separate to below anterior margin of 

 the eye; gill-rakers as long as pupil, 2-4+9-12. 



Dorsal spine slender, with very fine notches behind 

 and several large ones at the tip in front. Height of 

 the spine and rays very variable, sometimes twice as high 

 as the length of the fin. Dorsal spine midway between 

 snout and anal. Adipose fin very long, 2J in the length. 



Caudal cleft to near its base; the upper lobe sometimes 

 shorter than the head, sometimes as long as the head to 

 tip of humeral process. Ventrals IJ-lf in head. 



Pectoral spine strong, IJ-lf in the head, fine recurved 

 teeth behind, and a few much larger recurved teeth near 

 the tip. Caudal peduncle very broad, 2J-3 in head. 



Head 5; depth 6; Br. 7; D. I, 6; A. 12-15. 



