SOUTH AMERICAN NEMATOGNATHI. 141 



Body short, compressed; head broad, its width 1^- in 

 its length, its depth 1J; width of mouth at the rictus 

 2J; profile straight to above the eyes, decurved in front 

 of the eyes; interorbital region flat, postorbital convex 

 in transverse profile; occipital process not reaching to 

 the dorsal plate, covered with thick skin. 



Snout depressed, flattish; upper jaw projecting; teeth 

 of the upper jaw in a rather deep subcrescentic patch, 

 interrupted in the middle, the width of the band little 

 more than three in the head. 



Maxillary barbels reaching about to the adipose fin; 

 mental barbels little beyond eye; postmentals to base of 

 pectoral. 



Eye small, 5 in head, 2 in the snout, 1J in the inter- 

 orbital. 



Gill membranes separate to below the anterior portion 

 of the eye; humeral process extending about to middle 

 of pectoral spine. 



Dorsal spine equidistant between the snout and the 

 anal; entirely smooth in front, its length 1| in the head, 

 the longest dorsal ray 1|. 



Distance of adipose fin from the dorsal fin equals the 

 length of the dorsal fin; adipose fin about 4 in the 

 length. 



Caudal deeply lobed, the upper lobe longer, 4 in the 

 length. 



Anal fin sometimes extending beyond tip of adipose 

 fin, the longest ray 1^ in head. Ventrals 1^ in head. 



Pectoral spine 1| in head, its anterior margin almost 

 smooth, its posterior margin with about ten teeth, largest 

 along the middle third or half of the spine. 



Depth of caudal peduncle 2| in head. 



Color dark brown, everywhere with minute darker 

 dots; a dusky lateral band which is continued forward 

 on head in some specimens. 



