SOUTH AMERICAN NEMATOGNATHI. 47 



vv. Inuer margiu of palatine jDatclies of teeth concave, the 

 distance between them greater than the longitudinal 

 diameter of the eye. Fontanel gradually continued as a 

 groove. Grauiilations of head rather coarse, arranged in 

 series. Anterior margin of dorsal sj^ine with grannies. 



upsnlonophorus 43. 

 tt. Vomerine patches separate on the median line. 



ic. Spines scarcely shorter than head; head 4 in the length. 



osculus 44. 

 ivw. Spines low; head 3|-3| in the length. 



X. Teeth on palate in 4 patches, bluntly conical; vomerine 



patches oblong, separate from each other and from the 



palatine patches; palatine patches comparatively small; 



occipital process scarcely as long as broad, elaiturtis 45. 



XX. Teeth on palate in 6 patches, villiform; vomerine 



patches siibtriangiilar, separate but contiguous to the 



patches on palatines. Occipital process H times as long 



as broad. barbus 46. 



cc. Palatine patches of teeth without a backward projecting angle on 



the inner margin. 



A. Eye above the level of the mouth; gill-rakers 25 or' fewer. 



B. Teeth on the jaalate villiform. (Hexanematichthys.) 



C. Teeth on the palate in 4 patches; the vomer and palatine 

 patches sometimes contiguous. 



D. Granulations of the head not extending forward to between 

 the eyes. 

 E. Fontanel continued backward as a narrow groove. 



F. Head flat, depressed in front; snout scarcely decurved; 

 occipital keel bluntish; eye 7 in head, 3| in interocular 



width; granulations about the head coarse, conspiciious. 



seema7ini 47. 

 FF. Head scarcely de^aressed, the snoiit strongly decurved; 

 occipital keel sharper than in any other species; eye 5- 

 5J in head, 2f-3 in the interocular; granulations about 

 the head less distinct than in seemanni; jDalatine patches 

 of teeth much smaller. " jordani 48. 



EE. Fontanel not continued as a groove into the granu- 

 lated region of the head. 



G. Palatine patches of teeth small, scarcely larger than the 

 vomerine patches which are oval and widely separated 

 on median line; occiiiital process broader than long; 

 head three-fourths as wide as long; eye 6^ in head, 2 in 

 snout, 3 in the interocular sjjace; maxillary barbels reach 

 middle of pectorals; occipital process keeled, subtrun- 

 cate posteriorly; dorsal spine 2 in head; adipose fin 

 shorter than dorsal fin; upjjer caudal lobe almost as long 



