THE AMERICAN TETRAGONOPTERINAE. 79 



Head 4; depth 2.5; D. 11, counting the divided ray as 2; A. 26; scales 

 6-34-4. Eye equals twice the length of the snout, 2.4 in the head; interorbital 

 3 in the head. 



Compressed, dorsal and ventral profiles nearly equally curved, the ventral 

 more regularly; profile slightly depressed over eye; preventral area rounded, 

 postventral area compressed; predorsal area slightly keeled, with a median 

 series of ten scales from dorsal to occipital crest. 



Occipital process a little more than one fifth of the distance between its 

 base and the dorsal, bordered by three scales on each side; interorbital very 

 slightly convex; second suborbital leaving a naked area on cheek which is 

 widest below; maxillary not reaching to the end of the first suborbital, equal 

 to the distance from tip of snout to pupil. Five teeth in the front row of the 

 premaxillary, the third entirely withdrawn from the line of the rest; five gradu- 

 ated teeth in the inner series; two teeth on the maxillary; four graduated, large 

 teeth on each ramus of- the lower jaw followed by smaller ones on the side. 



Scales deeply imbricate, with a few not greatly divergent striae; anal 

 without a sheath (in this specimen only ?) ; caudal lobes covered with caducous 

 scales for at least half their length; lateral line scarcely descending in front. 

 Origin of dorsal equidistant from tip of snout and base of caudal, distinctly 

 further from tip of snout than the ventrals; ventrals equidistant from tip of 

 snout and base of penultimate anal ray, reaching not quite to anal, pectorals 

 to ventrals. Anal probably emarginate. 



A black line along the base of the anal; a faint dark line along the sides, 

 otherwise faintly silvery without spots. 



9. Moenkhausia oligolepis (Giinther). 

 Capaule of the Potaro Indians. 

 Plate 7, fig. 4; Plate 95, fig. 4; Plate 100, fig. 5. 



Tetragonoplerus oligolepis Gunther, Cat. fishes Brit, mus., 1S64, 5, p. 327 (British Guiana), Eigen- 

 mann & Eigenmann, Proc. U. S. N. M., 1891, 14, p. 53; Ulrey, Ann. N. Y. acad. sci., 1S95, 8, 

 p. 282; Vaillant, Bull. Mus. hist, nat, 1899, 5, p. 155 (Carnot). 



Moenkhausia oligolepis Eigenmann, Rept. Princeton univ. exped. Patagonia, 1910, 3, p. 437; Mem. 

 Carnegie mus., 1912, 6, p. 321, pi. 46, fig. 3. 



Tetragonoplerus agassizil Steindachner, Ichthyol. beitr., 1876, 6, p. 41, pi. 8, fig. 2 (Tabatinga; Cuda- 

 jas; Hyavary); Cope, Proc. Amer. philos. soc, 1878, 17, p. 691 (Peruvian Amazon); Eigenmann & 

 Eigenmann, Proc. U. S. N. M., 1891, 14, p. 53; Ulrey, Ann. N. Y. acad. sci., 1895, 8, p. 281. 



fAslyanax atahualpuanus Fowler, Proc. Acad. nat. sci., Phil., 1906, p. 436, fig. 36 (Pebas). 1 



f Moenkhausia alahualpiana Eigenmann, Rept. Princeton univ. Exped. Patagonia, 1910, 3, p. 437. 



•This species is said to have: Head 3.3; depth 2.75; D. 12; A. 24; lat. 1. 26-27. 



