SOUTH AMERICAN NEMATOGNATHI. 13 



touching the skin. Coracoid and humeral processes 

 large. Teeth villiform, in bands on the jaws, none on 

 the vomer; intestinal canal short. Derm naked. Mouth 

 terminal or subterminal, never truly inferior. Ante- 

 rior nares remote from the posterior, neither with a 

 barbel. Gill membrane joined to the isthmus, the gill- 

 opening reduced to a narrow slit in front of the pec- 

 toral. Dorsal short, placed over the ventrals. Pectoral 

 with a strong spine; anal very variable. 



Habitat: Whole course of the Amazons; Guiana. 



The Bunocephcdince are found in the upper and mid- 

 dle course of the Amazons and in Guiana, while the 

 Platystacince are found only in the lower course of the 

 Amazon (Para River) and in Guiana. 



ANALYSIS OF THE GENERA OF BUNOCEPHALIDJE. 



a. Tail short; vent nearly equidistant from tip of snout and base of caudal. 

 Anal with less than 10 rays. (BUNOCEPHALIN.E.) 



b. Dorsal vestigiary, of 2 rays only; barbels 6; head broad and de- 

 pressed, its depth less than that of the posterior portion of the com- 

 pressed tail; anterior margin of the pectoral spine smooth. 



BUNOCEPHALICHTHYS I. 



bb. Dorsal well developed, of 5 rays, the last of which is adnate; head 

 deeper than the posterior portion of the tail. 



c. Barbels 6. BUNOCEPHALUS n. 



cc. Barbels 2, on the maxillaries only. DYSICHTHYS in. 



aa. Tail long, with a median dorsal fold; distance of vent from tip of 

 snout less than half its distance from base of caudal. A. 50-60. 



(PLATYSTACINJS) PLATYSTACUS IV. 



SUBFAMILY BUNOCEPHALIN^. 

 I. BUNOCEPHALICHTHYS. 



Bunocephalichthys Bleeker, Nederl. Tijdschr. Dierk. i, 

 1863, 118, (hypsiurus). 



Type: Bunocephalus hypsiurus Kner. 



This genus is characterized by its rudimentary dorsal 

 fin. 



