SOUTH AMERICAN NEMATOGNATHI. 125 



The postmentals vary in length, their tips extending to 

 middle of the pectorals or as far as the middle of the 

 ventrals. Sometimes the barbels are much shorter on 

 one side than on the other. ' 



Mouth wide, terminal, the jaws usually equal, but the 

 lower sometimes considerably shorter. Teeth of the 

 lower jaw as usual, those of the upper in a very shallow 

 interrupted band; its depth 7-10 in its width. 



Gill rakers long and slender, simple, 2-1-8. 



Distance of dorsal fin from snout 2| to 3 in the length; 

 dorsal spine slender, pungent, with a few notches near 

 the tip in front; 2-2A in head; highest dorsal ray li-lj. 

 Distance of adipose fin from the dorsal fin variable, 

 always less than the length of the dorsal; adipose fin 

 2\-S in the length. 



Caudal cleft to near its base, the lower lobe broader 

 and rounded, 3h-4h in the length. 



Anal higher than long, the tips reaching to below the 

 vertical from the end of the adipose or sometimes two 

 diameters of the eye shorter. 



Ventral inserted below the vertical from the last dorsal 

 ray, Ih in head. 



Pectoral spine roughened with minute straight teeth 

 behind, and recurved teeth near the tip on the anterior 

 margin, Ih-ll in head. 



Color brown, a darker humeral spot; fins all dusky; 

 dorsal with the usual light transparent band, sometimes 

 with a black spot between the last two rays. The color 

 sometimes uniform black; sometimes very light brown. 

 Head 4-42- ; depth 41-7 ; depth above first ray SJ-G; 

 depth of caudal peduncle 8-10. 



Br. 7; D. I, 6; A. 9-12. 



The specimens examined, more than sixty, are from 

 Tonantins, Gurupa; Rio Janeiro; Bahia; Xingu; Santa 

 Cruz; Cudajas ; Sao Matheos ; Rio Doce; Serpa; Taba- 



