THE AMERICAN TETRAGONOPTERINAE. 



241 



reaching anal, their origin and the third scale in front of the dorsal equidistant 

 from the snout. Pectorals reaching the ventrals. 



Brassy; a silvery lateral band; no trace of a humeral spot; middle caudal 

 rays dark, the chromatophores scattered over the base of the neighboring rays. 



9. AsTYANAX (PoECiLURiCHTHYs) POLYLEPis (Giinther). 

 Plate 64, figs. 3 and 5. 



Tetragonopterus pohjlepis Gunther, Cat. fishes Brit, mus., 1864, 5, p. 320 (British Guiana); Eigen- 

 MANN & EiGENMANN, Proc. U. S. N. M., 1891, 14, p. 52; Ulrey, Ann. N. Y. acad. sci., 1895, 8, p. 

 276; EiGENMANN, Rept. Princeton univ. exped. Patagonia, 1910, 3, p. 432; Mem. Carnegie mus., 

 1912, 5, p. 356, pi. 41, figs. 2, 3. 



Habitat. — Guiana. 



Specimens examined. 



Readily distinguished by its circular spot over the 7-9 scales of the lateral 

 line and its small scales. 



Head 3.5^; depth 2 in the largest, 2.6 in the young; D. 11: A. 27-31^; 

 scales 10-42 to 46"-7 to 9 to ventrals; eye 3, interorbital 2.3 in the length of 

 the head. 



Much compressed, very deep in adults, the ventral profile pendant, the 

 dorsal regularly arched from the snout to the caudal peduncle; much more 

 slender in the young but maintaining the same ratio of curvature between 

 the back and belly. Preventral region narrowly rounded, the pectorals consid- 

 erably above the lower edge of the breast, scales of belly irregularly imbricate ; 

 postventral area narrowly compressed; entire back very narrow, not especially 

 keeled. Predorsal area naked to near the dorsal where there are a few median 

 scales or a few of the scales of one side lapping over the back. 



Occipital process one fourth of the distance from its base to the dorsal, 



1 Giinther gives the anal as 34 in the type. In twenty specimens examined two have 27 rays, four 

 have 28, eight have 29, four have 30 and two have 31. 



= In sixteen six have 42, six have 43, two have 44, one has 45 and one 46. 



