SOUTH AMERICAN NEMATOGNATHI. 41 



Distance of dorsal spine from tip of snout 2|-2f in the 

 length; dorsal spine stout, its inner margin with a few 

 recurved teeth near the tip, outer margin with granules 

 along its basal half, the upper half with recurved 

 notches; the height of the spine IJ-lf in the length of 

 the head; the highest ray 1-lf , the rays rapidly decreas- 

 ing backward, the last being less than half the height 

 of the first. Distance of adipose fin from the dorsal 

 3J-3J in the length, the adipose fin very short, 1J diam- 

 eters of the eye in length. 



Caudal deeply forked, the upper lobe narrower and 

 longer, 3J-4^ in the length. 



Free margin of the anal emargmate. 



Ventrals 2-2J in the head. 



Pectorals l^-lf in the head; pectoral spine stout, de- 

 pressed, about as high as the dorsal spine; outer margin 

 roughened, with recurved hooks near the tip becoming 

 obsolete in the adult; inner margin with saw-teeth in 

 small specimens, becoming more or less irregular in 

 large examples. 



Color blue-black; bluish silvery on sides below^the 

 lateral line, below smutty with dots, which, under the 

 lens, are seen to be pale blue encircled withfdark brown, 

 the ventral surface sometimes plain whitish; the fins 

 usually dark smutty. 



Head 3f~4; depth 6; Br. 6; D. I, 7; A. 18-19. 



IX. TACHISURUS. 



Tachisurus LacepMe, Hist. Nat. Poiss. v, 151, pi. v, 



fig. 2, 1803. 



Bagrus Cuv. & Val., Hist. Nat. Poiss., xiv, 1839 (sp.) 

 Galeichthys Cuv. & Val., 1. c. xv, 28, 1840 (sp.) 

 Galeichthys Bleeker, Nederl. Tijdschr. Dierkunde, i, 



1863, 90 (feliceps). 



Arius Cuv. & Val., Hist. Nat. Poiss. xv, 52, 1840 (sp.) 



