SOUTH AMERICAN NEMATOGNATHI. 123 



Depth, behind the humeral process, less than the width, 

 tapering to the caudal peduncle. Head depressed, as wide 

 as long. Frontal fontanel not continued behind the eye; 

 an elongate occipital fontanel. Occipital process short, 

 but meeting the longer dorsal plate. Large round pores on 

 the head, most numerous on the snout and chin. 



Eye small, 2| in the snout, 8.^ in the head, 3 in the in- 

 terorbital. 



Barbels all short, those of the maxillaries extending 

 about to middle of pectorals. Mouth more than half as 

 wide as length of head; iuterniaxillary band of teeth with 

 a sharp, backward projecting angle; mandibulary band of 

 teeth shallower than the intermaxillary band, about as deep 

 as one diameter of the eye, scarcely widened in front. 



Humeral process nearly horizontal, strong, triangular, 

 not reaching middle of pectoral fin. 



Distance of dorsal fin from tip of snout 2^ in the length; 

 the dorsal spine stout, toothed on its outer margin, 2 in head, 

 the rays higher, nearly uniform. Distance of adipose fin 

 from the dorsal more than the length of the dorsal fin; the 

 adipose about as long as the dorsal fin. 



Caudal fin long, scarcely shorter than the head, rounded. 



Anal fin beginning and ending a little in advance of the 

 anterior and posterior ends of the adipose; the tips of the 

 anal rays reaching base of caudal fin when laid back. 



Ventrals inserted under the vertical from last dorsal ray, 

 1J-1| in the head. 



Pectoral fin extending to the ventrals in young, much 

 shorter in adult specimens, the spine 1^ in head, little 

 shorter than the longest ray, very much depressed, the 

 teeth equally strong and long on both margins, those on 

 the outer margin directecV toward the tip, on the inner 

 margin toward the base of the spine. 



Abdominal region sometimes covered with small papilla?; 

 anterior portion of the lateral line with larger papillae or 



