SOUTH AMERICAN NEMATOGNATHI. 181 



The numerous specimens in the museum are from 

 Para. 



Body deeper than wide, compressed towards the cau- 

 dal; head flat below, regularly convex in a cross-section 

 above; profile straight or making a decided angle at the 

 base of the occipital crest; width of the head about 

 If in its length, its width at the angle of the mouth 3; 

 its depth 1|; entire upper portion of head granulate or 

 striate; fontanel wedge-shaped, its broad base opposite 

 the posterior margin of the eye. Occipital crest narrow; 

 its width at the base 2 in its length; its tip truncate. 



Distance between the anterior and posterior nares 

 equal to the diameter of the eye. 



Maxillary barbel reaching far beyond tips of caudal; 

 mental barbels to middle of pectoral, postmentals beyond 

 tip of ventral. 



Eye very small, 5|-6 in head, 2i-3 in snout, 1^ in 

 interorbital, 2 diameters behind angle of mouth. 



Mouth narrow, distinctly inferior, the upper jaw pro- 

 jecting beyond the lower for at least half the diameter 

 of the eye; depth of mandibulary band of teeth 2 in eye; 

 intermaxillary band scarcely deeper, its depth 5 to 6 in 

 ts width; numerous minute pores about the snout. 



Gill-membranes separated by a deep notch to in front 

 of the eye; gill-rakers 5+10, the first two arches with a 

 single series and a membrane, the third and fourth with 

 two series. 



Dorsal spine 1| in head, with sharp, short teeth be- 

 hind; longest dorsal ray about as long as the head; the 

 spine equidistant from snout and tips of ventrals, measur- 

 ing in a straight line. 



Interspace between the dorsals reduced to a minimum. 



Adipose dorsal long and low, 2| in the length. 



Caudal very deeply forked, the outer rays about five 

 times as long as the middle rays, twice as long as the 

 head. 



