

SOUTH AMERICAN NEMATOGNATHI. 47 



vv. Inner margin of palatine patches of teeth concave, the 

 distance between them greater than the longitudinal 

 diameter of the eye. Fontanel gradually continued as a 

 groove. Granulations of head rather coarse, arranged in 

 series. Anterior margin of dorsal spine with granules. 



upsulonophorus 43. 

 it. Vomerine patches separate on the median line. 



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



osculus 44. 

 iviv. Spines low; head 3f-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, elatturus 45. 



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



patches subtriangular, separate but contiguous to the 



patches on palatines. Occipital process 1J 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 palate villiform. (HEXANEMATICHTHYS.) 



(7. 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, conspicuous. 



seemanni 47. 



FF. .Head scarcely depressed, the snout strongly decurved; 

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

 5 1 in head, 2-3 in the inter*ocular; granulations about 

 the head less distinct than in seemanni; palatine 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; occipital process broader than long; 

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

 snout, 3 in the interocular space; maxillary barbels reach 

 middle of pectorals; occipital process keeled, subtrun- 

 cate posteriorly; dorsal spine 2 in head; adipose fin 

 shorter than dorsal fin; upper caudal lobe almost as long 



