Eigenmann: The Serrasalmin.e and Mylin/E. 241 



Key to the Species of Rooseveltiella. 

 a. Cheeks fully covered by the second suborbital except in the young. 



b. Abdominal serrae 40; depth about 2 in the length; interorbital a little less 

 than one-half the length of the head; second infra-orbital touches the 

 pre-opercle; distance between dorsal and upper caudal fulcra much 

 longer than base of dorsal; gill-rakers of the outer branch very short 



and broad. D. 18; A. 33-35; lat. line 105 niger (Schomburgk). 5. 



bb. Abdominal serrae fewer than 40. 



c. Distance between dorsal and upper caudal fulcra less than the base 

 of the dorsal, equal to the postorbital portion of the head, or shorter; 

 origin of dorsal about equidistant between anterior margin of eye 

 and end of lateral line; base of anal shorter than head;D. 16-19; 

 A. 27-31; serrae 22-38; interorbital 2.1 in head; depth 1.87-2. 



natter eri (Kner). 6. 

 cc. Distance between dorsal and upper caudal fulcra equal to, or a little 

 greater than, the base of the dorsal, equal to the postorbital portion 

 of the head; origin of dorsal equidistant between end of lateral line 

 and snout or origin of eye; base of anal equal to length of head in 

 the younger; equal to head without opercle in the old; interorbital 

 2-2.23 in the head; head 3.3-3.25; depth 1.8-2.2. 



notatiis (Lutken). 7. 



aa. Cheeks with a very narrow naked margin. 



d. No well defined humeral spot; distance between dorsal and upper caudal 

 fulcra about equal to the length of the base of the dorsal, a little greater 

 than the postorbital portion of* the head; origin of dorsal nearer base 

 of upper caudal rays than eye; base of anal equal to length of head less 

 half of the opercle; D. 17; A. 23; serrae 26; interorbital 2.2 in the head; 



depth 1.8 altus (Gill). 8. 



dd. A large conspicuous humeral spot; space between dorsal and caudal 

 longer than the dorsal, equal to head without opercle; base of anal 

 shorter than head; second suborbital as high as long; D. 18 or 19; 

 A. 30; serrae 28; interorbital 2.25 in the head; head 3.33; depth 1.9; 

 sides spotted, caudal margined with dark. 



stigmaterythrceus (Fowler). 9. 



5. Rooseveltiella niger (Schomburgk). (Plate XLV.) 

 Serrasalmo niger Schomburgk, Fishes Brit. Guiana, Vol. I, 1841, p. 222, tab. 18 

 (in streams between forty and fifty miles from coast); GDnther, Cat. Fishes 

 Brit. Mus., Vol. V, 1864, p. 369. 

 Pygocentrus niger Muller & Troschel, Horae Ichthyol., Vol. I, 1845, p. 21, tab. 2, 

 fig. 3; ? CuviER & Valenciennes, Hist. Nat. Poiss., Vol. XXII, 1848, p. 286 

 (Corentyn); Mijller & Troschel, in Schomburgk, Reisen. Vol. Ill, 1848. 

 p. 636 (upper courses of all streams of Guiana); Eigenmann & Eigenmann, 

 Proc. U. S. Nat. Mus., Vol. XIV, 1891, p. 59; Eigenmann, Reports Princeton 

 Univ. Exp. Patagonia, Vol. Ill, 1910, p. 442; Mem. Carnegie Mus., Vol. V, 

 1912, p. 384. 



