eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 319 



Key to the Guiana Species of Tetragonopterus. 



a. A. 36; scales in front of dorsal crowded, about fifteen in the median line; occipital process bordered by 

 seven scales on each side; caudal scaled on its basal part only; scales 8-33-4; head 3.33; depth 1.70; 

 eye 2.3 in head, .8 in interorbital; pectoral extending three scales beyond origin of ventrals; a black 



bar across base of caudal; two oblique bars across anterior part of sides argenteus. 



aa. A. 31-33; scales in front of dorsal normal, eight or nine in the median line; occipital process bordered by 

 four scales; caudal more densely scaled; scales 7 or 8-33-3.5; head 3.66; depth 1.7-2; eye 2.33; inter- 

 orbital 2.5 in the head; pectoral extending to the ventrals or one scale beyond them; a black spot or 

 bar at the base of the caudal; two faint oblique bars across anterior part of the sides chalceus. 



Fig. 38. Tetragonopterus chalceus Agassiz. No. 20718 Mus. Comp. Zool. 



173. Tetragonopterus argenteus Cuvier. 



Tetragonopterus argenteus Cuvier, Mem. Mus. d'Hist. Nat., IV, 1818, 455. — Muller 

 and Troschel, in Schomburgk, Reisen, III, 1848, 634 (Amucu). — Kner, 

 "Familie der Oharacinen," i, 1859, 38 (Cajaba; Guiana). — Steindachner, 

 "Flussfische Si'idamerika's," i, 1879, 7 (Orinoco near Ciudad Bolivar).— 

 Eigenmann, Repts. Princeton Univ. Exp. Patagonia, III, 1910, 438. 



Tetragonopterus rufipes Valenciennes, in d'Orbigny, Voy. Am. Mer., V, ii, 1847, 

 pi. 2, fig. 2. 



Tetragonopterus sawa Castelnau, Anim. Am. Sud, Poiss., 1855, 65, 'pi. 33, fig. 

 1 (Rio Coxas). 



Tetragonopterus chalet ns mot of Agassiz) Eigenmann and Kennedy, Proc. Acad. 

 Nat, Sci. Phila., 1903, 523. 



