THE AMERICAN TETRAGONOPTERINAE. 91 



ray when depressed reaching the base of the last but four anal ray; ventrals 

 reaching anal, pectorals about one scale beyond origin of ventrals. 



No caudal spot, a large horizontally oval humeral spot continued below 

 to the origin of the pectoral; a dark band from origin of dorsal obliquely down- 

 ward and forward to the lateral line; a dark median lateral line; white below, 

 dark along back, each scale of the side with a conspicuous dark crescent along 

 its middle. 



In life all fins but the adipose strongly tinged with red; middle of adipose 

 yellow. 



16. Moenkhausia megalops Eigenmann. 

 Plate 7, fig. 2. 



Tclragonopterus grandisquamis Ulbey (non Miiller & Troschel), Ann. N. Y. acad. sci., 1895, 8, p. 281 



(Itaituba). 

 Astyanax megalops Eigenmann, Proc. U. S. N. M., 1907, 33, p. 29 (Itaituba, Brazil). 

 Moenkhausia megalops Eigenmann, Rept. Princeton univ. exped. Patagonia, 1910, 3, p. 438; Mem. 



Carnegie mus. 1912, 5, p. 325 (Rockstone). 



Habitat. — Amazon and Guiana. 



Specimens examined. 



Allied to M. grandisquamis with different proportions and different striae, 

 with larger eye. 



Head 3.6-3.7; depth 2.5-2.66; D. 9-11; A. 28-30; scales 5-34-3 or 4. 

 Eye 2-2.2 in head, twice as long as snout ; interorbital 2.8-3 in the head. 



Elongate, compressed, dorsal and ventral profile evenly curved, a slight 

 depression over eye; preventral region with a median series of flat scales bor- 

 dered by a series of scales angularly bent ; postventral region compressed, with a 

 median series of large, thin scales, bordered on each side by slightly asymmetri- 

 cal scales; predorsal region compressed, the median series of eight scales extend- 

 ing from the dorsal to the occipital crest which is contained three to three and a 



1 To base of caudal. 



