SOUTH AMERICAN NEMATOGNATHI. 49 



LL. Sides of the dorsal and pectoral spiues striate; fontanel 

 broadly rounded behind; intermaxillary band of teeth six 

 times as wide as deep; palatine patches U diameters of eye 

 in width and length. rugispinis jihrtjgiatus 55a. 



KK. Eye very large, 4i- 5 in head, lJ-2 in iuterocular; fon- 

 tanel contiuiied as a groove. grandoculis 56. 

 BB. Teeth on the palate granular; no teeth on vomer; gill mem- 

 brane not forming a free margin across the isthmus.* 



„ , , „, (TACHisuRus=^r«wsBleeker '58.) 



M. Anal rays 23 or fewer. 



N. Head as broad as high; its width \\ in its length. 



0. Head 4, A. 21; teeth large, granular. Occipital ^jrocess 

 triangular, as long as broad, obtusely keeled; groove of the 

 fontanel not reaching base of occipital process; palatine 

 teeth in two subtriangular patches which sometimes meet 

 in front. Maxillary barbels extending to near tip of pec- 

 torals. Dorsal spine slightly serrated along both edges, ^ 

 as long as head; adipose fin shorter than the dorsal fin; pec- 

 toral spine as long as, but stronger than the dorsal spine. 

 Depth5; D. I, 7; A. 21.t (Giinther). 

 00. Head 3^; A. 19. Teeth rather small, bluntly conical. 



nuchalis 57. 

 NN. Head broader than high. agassizii 5% 



P. Soft portions of the head not pitted. 



Q. Head 3 in the length; maxillary barbels reaching almost 

 to the middle of the pectoral fin.t Jissus 59. 



QQ. Head more than 3 in the length. 



R. Axillary pore as large as a nasal opening. Dorsal 

 spine equal to distance between front of eye and gill 

 opening; pectoral spine nearly as long and strong as 

 the dorsal spine; groove of fontanel scarcely reaching 

 base of occipital process; inner surface of pectorals 

 blackish. Head 4^; depth 5; D. 1, 7; A. 21.$ (Giinther.) 



melanopus 60. 

 RR. Axillary pore much smaller than a nasal opening. 

 S. Pectoral spine reaching halfway to the posterior 

 third of the ventrals, or shorter; upper jaw projecting; 

 posterior margin of the eye about in the middle of the 

 head. Occipital process greatly narrowed behind, its 

 width at tip not more than half a diameter of the eye. 

 Teeth on the jmlate large, granular, 20 or fewer, some 

 of the posterior ones usually much enlarged. 



fipixli 61. 



*The last point examined only in spixii, fiirthi and agassizii. 



tBaaed on specimens .15 m. long. tBased on specimens .15 m. long. 



?Based on specimens .20-. 23 m. long. 



