SOUTH AMERICAN NEMATOGNATKI. 287 



Elongate, compressed, the depth everywhere much 

 greater than the width. Head somewhat pointed, its 

 greatest width 1| in its length; its width at the rictus 

 more than 2; its depth at base of occipital process greater 

 than its width, about 1^- in the length; transverse profile 

 of posterior part of the head strongly arched; the head 

 everywhere covered with loose skin, the surface of the 

 bones not exposed; frontal bones not swollen nor honey- 

 combed; frontal fontanel open in front, extending back- 

 ward to the center of the eye. Dorsal plate much as in 

 nodosH.'^, its posterior pocess extending a little farther 

 back than in nodosits. 



Eye oval, its anterior margin in front of the rictus, 

 3i in the head, 1| in the interocular, its diameter greater 

 than the length of the snout. 



Maxillary barbel scarcely reaching to the middle of 

 the pectoral; mental barbel about as long as the eye, 

 postmental not reaching base of pectoral. 



Snout narrow, rounded; lower jaw included; teeth all 

 villiform, the intermaxillary band strongly arched, its 

 depth about 7 in its width. 



Gill-opening extending to the base of the pectoral fin. 

 Humeral process smooth, about reaching middle of pec- 

 toral spine. Pectoral pore rather large, round. 



Lateral line undulating. 



Distance of the dorsal spine from snout 3|-3| in the 

 length; dorsal spine li-l| in the head, its outer margin 

 scarcely roughened, its inner margin with short teeth; 

 first soft ray higher than the spine. Distance between 

 dorsal and adipose fins 2|-2| in the length. 



Caudal fin deeply forked, the lobes pointed, 31 in the 

 length. 



Anal fin emarginate, the tips of the anterior rays in 

 the 2 not reaching base of last; in the S reaching beyond 

 the last ray. 



