SOUTH AMERICAN NEMATOGNATHI. 189 



Body rapidly tapering towards caudal; head heavy, 

 broad, flattened between the eyes; greatest width of the 

 head equals its length; width at the angle of the mouth 

 2 in its length. 



Eye 9 in head, 3 in snout; 5 in interorbital; 2 diam- 

 eters behind the rictus. 



Maxillary barbel on edge of lip, opposite anterior nos- 

 tril, reaching beyond the tips of the pectoral fin; mental 

 barbels J as long as postmental barbels, which reach 

 the pectoral. 



Lower jaw included; teeth all alike; those on the in- 

 termaxillaries in a broad 

 band of equal depth through- 

 out; vomerine teeth in a 

 much broader patch; pala- 

 tine teeth in narrower 

 wedge-shaped patches con- 

 tiguous to the vomerine 

 patch. 



Gill-membranes separate to below anterior margin of 

 the eye. Gill-rakers short and fleshy, 4+15. 



Bones behind eye variously grooved and granulated; 

 the occipital process broadly rounded behind, not meet- 

 ing the reniform dorsal plate. 



Dorsal spine midway between snout and tip of adi- 

 pose dorsal, and between bases of pectoral and ventral 

 fins; last dorsal ray over base of ventral, the length of 

 the spine 2J in head. 



Adipose dorsal short, high, its upper portion generally 

 transformed into true rays; its base longer than that of 

 the anal. 



Caudal broad, slightly emarginate. The rays of the 

 dorsal and caudal thick and terete, once or twice 

 branched. Ventrals extending for half their length 

 beyond the vent. 



