SOUTH AMERICAN NEMATOGNATHI. 49 



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

 broadly rounded behind; intermaxillary band of teeth six 

 times as wide as deep; palatine patches 1 diameters of eye 

 in width and length. rugispinis phryqiatus 55a. 



KK. Eye very large, 4 - 5 in head, If -2 in interocular; fon- 

 tanel continued 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= Arius Bleeker '58.) 

 M . Anal rays 23 or fewer. 



N. Head as broad as high; its width 1| in its length. 



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

 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. 

 Depth 5; 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 58 



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. 



7?J?. 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 palate large, granular, 20 or fewer, some 

 of the posterior ones usually much enlarged. 



spixii 61. 



*The last point examined only in spixii, f'urthi and agassizii. 



t Based on specimens .15 m. long. {Based on specimens .15 m. long. 



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



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