SOUTH AMERICAN NEMATOGNATHI. 14T 



Elongate, slender, the width scarcely less than the depth. 

 Head broad, strongly depressed, the profile to tip of snout 

 nearly straight; greatest width of head li in its length, its 

 dej)th at base of occipital process about 2. Occipital pro- 

 cess about as broad as long, obtusely keeled. Fontanel 

 very narrow, its center above the posterior margin of the 

 eye, continued backward as a groove. Top of head rugose 

 posteriorly. Four bony ridges between the eyes, the inner 

 two margining the fontanel, the outer extending obliquely 

 backward from near the posterior nostrils; sides of head 

 and snout with reticulating canals. 



Eye oblique, its center over the posterior end of the man- 

 dible and about on a level with the rictus, its diameter 2|^ 

 in snout, 8 in head, 5 in the interocular distance. 



Maxillary and post-mental barbels reaching to the middle 

 of the pectoral fins or shorter; mental barbels to near base 

 of pectoral. 



Jaws sub-equal, very thin; intermaxillary band of teeth 

 very shallow in the middle; no teeth on the vomer; the 

 space between the palatine patches equals IJ diameters of 

 the eye, the teeth obtusely conical, in about three series in 

 front, in a single series behind; mandibulary band of teeth 

 little more shallow than the intermaxillary band. 



Gill membranes united and having a free margin. Gill- 

 rakers li times as long as the eje, 12-j~30. 



Pectoral pore large; vertical series of pores on sides of 

 the body conspicuous. 



Distance of dorsal fin from snout 2J in the length ; dorsal 

 spine rather slender, high, 1^ in head; distance of adipose 

 fin from the dorsal 3| in the length; adipose fin as high as 

 as long, its posterior margin wholly free. 



Lower caudal lobe somewhat the broader, the upper lobe 

 I5-II in the head. 



Anal fin emarginate, the higliest ray 2| in the head. 



Ventral fins truncate, 21-21 in the head. 



Pectoral spine If in the head, its outer margin roughened; 

 its inner margin with recurved teeth. 



