SOUTH AMERICAN NEMATOGNATHI. 167 



shield-shaped dorsal plate. Distance between the nos- 

 trils equal to § the diameter of the eye. 



A deep groove from maxillary barbel to below eye, the 

 barbel reaching in No. 7574 beyond the caudal, in the 

 longest specimen, No. 7478, to the base of the adipose 

 dorsal; postmental barbels inserted behind and outward 

 from the mentals; mental barbels extending to base of 

 pectorals, slightly shorter in adult; postmentals not to 

 tip of pectoral. 



Eye large, 5 to 6 in the head, 2 to 2i in the snout, 

 l|-2 in interorbital region, 1| diameters behind the 

 rictus. 



Jaws subequal, the upper a little longer; width of the 

 mouth 2i in length of head; both lips papillose; teeth of 

 the lower jaw in a band equal to I the diameter of the 

 eye in depth, tapering to behind the rictus; a broad 

 papillose membrane behind it which is not much broader 

 at the rictus; teeth of the upper jaw in a band scarcely 

 deeper than the band of the lower jaw, not interrupted 

 at the middle; the band of the lower jaw broadly inter- 

 rupted at the middle; chin and snout with numerous 

 pores. 



Gill-membranes separate to nearly underneath the 

 rictus; gill-rakers overlapping, 2+12, in a single series 

 on the first two arches, the inner series being replaced 

 by a scalloped membrane. 



Dorsal spine rather weak, 1-^ in head, the highest ray 

 11 in head, the free margin of the fin rounded; the basal 

 fulcrum strong, the spine inserted forward of the middle 

 between base of pectoral and of ventral fins, equidistant 

 from snout and beginning of the anal fin. Adipose fin 

 long, 3-3| in the length. Caudal fin obliquely rounded, 

 the lower portion longer, 11 in head. 



Anal with its free margin narrowly rounded, the 

 eighth ray highest, 2 in head, the base of the fin equal 

 to two-thirds its height. Ventrals If in head. 



