SOUTH AMERICAN NEMATOGNATHI. 371 



than its length to upper angle of gill-opening; head 

 without ridges or keels, occipital region regularly con- 

 vex; occipital terminating in a broad, triangular pro- 

 cess which is margined by 2 nuchal plates; interorbital 

 slightly concave; snout broad, rounded, its entire mar- 

 gin narrowly naked. 



Orbital notch large, similar to that of L. riKicidatits, 

 diameter of orbit with its notch 4j-5 in the head. Eye 

 3j-4i in snout, 6|-9 in head, l|-2 in the interorbital. 



Lower surface of head naked except a narrow marginal 

 band. 



Teeth few, minute, in both jaws. Lower lip and the 

 sides of upper lip slightly fringed; the male with the 

 lower lip greatly expanded, reaching beyond base of pec- 

 toral fins. 



Anal plate pointed in front, margined by 2-4 plates; 

 belly with 3-5 series of plates; breast with smaller plates 

 of irregular shape; nuchal plates faintly bicarinate. 

 Lateral keels prominent, remaining separate throughout, 

 approximated on the 17th or 18th plate. 



Distance of dorsal fin from tip of snout 3 in the 

 length; first dorsal ray about equal to length of head. 

 Caudal obliquely truncate, the upper lobe longer. Anal 

 lower than the ventral; third ventral ray highest, reach- 

 ing beyond origin of anal. 



Pectoral short, reaching to ventrals. 



Brown, mottled with darker on the back; a series of 

 blotches between the lateral keels; posterior half of each 

 inter-radial dorsal membrane dusky, spotted with darker. 

 Caudal spotted with black, anal plain or somewhat spot- 

 ted; pectorals and ventrals dusky or blackish, the upper 

 surfaces profusely spotted with darker, the spots usually 

 forming cross-bars. 



Head 4^-4;Lat. 1. 30-31. 



Fourteen specimens .10-. 25m. Santarem; Hyavary; 



