SOUTH AMERICAN NEMATOGNATHI. 119 



dd. Jaws equal, or the upper jaw longer. 



f. Intermaxillary band of teeth of about equal depth throughout. 

 (j. No dark lateral band. 



h. Pores on the head not aggregated, or at most, 3 in a place; 

 D. I, 6, except sometimes in quelen. 



L Maxillary barbels extending beyond middle of adipose tin 

 in the adult. 



j. Vent midway between the bases of caudal and pectoral 

 fins; depth above first anal ray 4 in the length; depth 

 of caudal peduncle 8 in the length; base of anal oblique. 

 Maxillary barbels extending beyond base of caudal fin. 



obesus 82. 



jj. Vent midway between base of caudal fin and eye. Body 

 rather elongate; depth above first anal ray about 6 in 

 the length. Eye smaller, about 7 in length of the head. 



sebce 83. 

 jjj. Eye large, 3| (in young) 6 in the head. 



sebce kneri 83a. 



ii. Maxillary barbels not extending to middle of adipose fin 

 in the adult. 

 k. D. I, 5-8. 



L Adipose fin 3-4 in the length. 



m. Eye situated in the middle of the head. Inter- 

 ocular equal to one-half diameter of eye. Posterior 

 nasal opening nearer eye than to the snout. Head 

 flat, the eyes superior; occipital process very short. 

 Maxillary barbels reaching tips of pectoral fins; post- 

 mental barbels to base of pectorals. Dorsal spine 

 little more than half as high as the rays; adipose fin 

 originates above tips of ventrals, twice as long as the 

 dorsal fin; caudal forked, upper lobe longer than the 

 lower; anal under middle of adipose; pectoral spine 

 strongly serrated, especially along its outer margin. 

 Head more than 5 in the total length. Br. 6; D. I, 6; 

 A. 11. (Miiller & Troschel.) foina 84. 



mm. Eye in the anterior half of the head. 



n. Distance of adipose from dorsal fin equals f-f its 

 own length. Maxillary barbels extending on to 

 root of ventrals; intermaxillary band of teeth 8 

 times as wide as deep; eye 2-3 in interocular, 6 in 

 head; the eye occupies the third sixth of the head. 

 Pectoral spine 2| in head, slightly serrated along 

 both edges; caudal fin cleft to the base, the upper 

 lobe more pointed than the lower. Head 4f in the 

 length; depth 6; D. I, 6; A. 12. (Giinther.) 



humilis 85. 



