SOUTH AMERICAN NEMATOGNATHI. 99 



ii. Orbit withont a free margin; eye small; dorsal with- 

 out a pungent spine. 

 j. A. 18-20. 



k. Caudal obliquely rounded. Heptaptertjs xvii. 



kk. Caudal widely forked. A cextronichthy.s xviii. 

 jj. A. 8; dorsal entirely behind the ventrals. 



NaNNOGLANIS XIX. 



gg. Occipital process uaiTow, reaching the dorsal plate; 

 fontanel continued to base of occipital process, with a 

 bridge across it, above the posterior margin of the eye. 

 Dorsal and pectoral spines strong. Humeral process spine- 

 like. D. I, 6. PiMELODELLA XX. 

 aa. Teeth on vomer none, or in minute patches. 



I. Adipose fin longer than high. Head granulated above, naked or par- 

 tially naked; occipital process usually tapering to the dorsal plate; 

 fontanel not continued behind the eyes. Humeral process broad, not 

 spine-like. Pimelodus xxr. 



U. Barbels compressed, ribbon-like; occipital process not reaching the 

 dorsal plate (Gen. ? One species, agassizii, not seen). xxii. 



III. Adipose fin higher than long; head compressed; snout produced, 

 pointed; occipital process reaching the dorsal plate; fontanel con- 

 tinued to near the occipital process. Humeral process long, spine- 

 like. Anal rays 19 or 20. Conorhynchos xxiii. 

 aaa. Teeth on vomer in moderate or large patches or bands. 

 m. Upper jaw little, if at all, projecting beyond the lower. 

 n. Head more or less conical, about as high as wide. D. I, 6. 



0. Top of head striate. Vomerine teeth in two separate patches 

 which are remote from the palatine patches. Fontanel not con- 

 tinued behind the eyes; occipital process reaching the large dorsal 

 plate (closely related to Psecdariodes). Bagropsis xxiv. 



00. Top of head granulated. "Vomerine and palatine teeth form- 

 ing a continuoias band. Fontanel continued to near base 

 of occipital process; occipital j^rocess scarcelj' reaching the dorsal 

 plate. Barbels flattened. Piramutana xxv. 



nn. Head broader than deep, flattened, not conical. 

 p. Barbels very broad, flattened, band-like. Palatine teeth none; 

 vomer with a band of villiform teeth; jaws with very broad bands of 

 teeth. Occipital process reaching the dorsal plate. Dorsal spine 

 produced. Platynematichthys xxvi. 



pp. Barbels not band-like. 



q. Head as broad as long. D. I, 7. Upper surface of head with 

 vermiculating ridges. Vomerine patch of teeth large, penta- 

 gonal, contiguous to the palatine iiatches. Occipital i^rocess 

 large, semicircular, not meeting the reniform dorsal plate. 

 Upper half of the adipose fin usually rayed. 



Phractocephalus xxvii. 



