SOUTH AMERICAN NEMATOGNATHI. 105 



process. Occipital process very narrow, extending to near 

 the dorsal plate. 



Eye small, its center behind the middle of the head, 

 its diameter 3J-4 in the snout, 7J-9 in head, 2J-3 in the 

 interorbital. 



Maxillary barbels extending to, or nearly to the anal, 

 mental barbels to the middle of the ventral fin, postmen- 

 tal about as long as the maxillary barbels, all the barbels 

 flattened and margined posteriorly, with a broad mein- 

 branaceous border. 



Mouth wide, the gape extending more than half way 

 to the eye; teeth of both jaws very minute, those of the 

 mandible in a band one-half as deep 

 as the diameter of the eye, inter- 

 rupted in the middle; a strongly 

 arched band of teeth in the upper 

 jaw, seven times as wide as deep. 

 Branchiostegal membranes separate to in front of the 

 rictus; gill-rakers 7-|-17. Distance of the first dorsal 

 ray from tip of snout 3J-3f in the length. First 

 dorsal ray not pungent, continued in a filament, which 

 is equal in height to its distance from the snout, the rays 

 rapidly decreasing in height, the last ray one-third the 

 length of the first divided ray. 



The distance of the adipose fin from the dorsal equals 

 less than one-half the length of the latter. 



Adipose fin 2| 2-|- in the length. 



Caudal lunate in the smaller specimen, the longest 

 rays being shorter than the head; 4J in length of 

 body; deeply forked in the larger specimen, the longest 

 rays being one-third longer than the head, 3| in the 

 length . 



Free margin of the anal emarginate, the third ray ex- 

 tending beyond the tips of the last; more than half the 

 length of the head. 



