Eigenmann : New Characins in Carnegu Ml MM. 171 



HYSTE R0N01 i S 8 gen. no\ . 



(Type, Hysteronotus megalostomus sp. nov.) 



Mouth large, premaxillary teeth in two distincl series; five or more 

 teeth in the inner series of the premaxillary; second suborbital cover 

 ing the entire cheek: caudal apparently without glandular scales; 

 lateral line complete; adipose fin present; origin of dorsal nearer to 

 caudal than to eye, considerably behind the vertical from the origin 

 of the anal. 



This genus stands unique in the Tetragonopterina in the extreme 

 backward position of its dorsal. In this character it approaches some 

 of the Aphyocharacincs, from which its teeth sharply distinguish it. 



7. Hysteronotus megalostomus sp. nov. 



Plato VI, fig. I. 



Type- One specimen, 45 nun. C. M. No. 3551. Rio das Velhas, May 10, 1908. 

 1 pes.— Six specimens, 27 to 40 mm. C. M. No. 3552. Same place and date. 



Head 4: depth 3.33; D. 10; A. 35-36; scales 7-42-5 to ventrals, 

 about 8 to anal; eye 3, interorbital 2.6 in the head. Compressed, 

 short-snouted; pectorals falcate; chest somewhat ridged, approaching 

 on one side some of the Characince and on the other some of the 

 Aphyocharacincs in appearance. 



Ventral area narrowly rounded; predorsal area rounded, with about 

 twenty-five scales, not definitely arranged in a median series; occipital 

 process forming a nearly equilateral triangle, its length about one- 

 twelfth of the distance from its base to the dorsal, bordered on the 

 side by two scales; fontanels reduced to a just perceptible slit, except 

 at the base of the occipital process, where the parietal fontanel is an 

 equilateral rhomboid, of which the two margins of the occipital process 

 form two sides; interorbital with lateral grooves, scarcely convex in 

 the middle; second suborbital in contact with the lower margin of 

 the preopercle along its entire length, a narrow naked corner behind 

 it- upper posterior angle; mouth large, the premaxillary-maxillary 

 border forming a continuous curve whose length is about half the 

 length of the head. Snout pointed, premaxillary with an outer row 

 of three teeth and an inner row of six or seven; maxillary quite 

 slender, with three or four teeth; dentary with five or six larger teeth 

 and a number of smaller ones on the sides; of the larger ones the first, 



*"£<TTep4u = to come late; pwtos = the back. 



