191-4.] NATURAL SCIENCES OF PHILADELPHIA. 247 



Color in alcohol largely pale brownish, upper or dorsal region 

 very slightly darker, and lower surface paler. Head brownish 

 above, paler below. Lips pale brown. Eye slaty. Level with 

 upper part of eye, or on vertebral axis, a blackish humeral blotch, 

 a little deeper than wide, and distant from head 5 scales. All about 

 humeral blotch a pale area, best understood on examining figure. 

 Several scales posterior a narrow dusky streak begins and runs 

 along vertebral axis, and though gradually enlarging to caudal base, 

 not forming spot on latter. Fins all pale or whitish, dorsal and 

 caudal tinged with grayish. 



Length 95 mm. 



Type, No. 39,330, A. N. S. P. Rupununi River, British Guiana. 

 J. Ogilvie. 



No. 39,331, paratype, same data. Head 3f ; depth 2; D. iii, 9; 

 A. IV, 23, i; scales 33 in 1. 1. to caudal base, and 2 more on latter 

 8 scales above 1. 1.; 6 scales below 1. 1. to ventral origin; 7 scales 

 below 1. 1. to anal origin; 10 predorsal scales; snout 4 in head; eye 

 3iVj maxillary 2f ; interorbital 2f ; length 95 mm. 



Apparently a form of Moenkhausia ckrysargyrea (Giinther),^^ 

 though it is incompletely described. No mention is made of the 

 pale area surrounding the humeral blotch, and the dark posterior 

 lateral vertebral streak. That this color pattern should have 

 resulted from preservation originally in formaline may be likely 

 in the first case, though less so in the last. 



(J £0X09, white; t-cu,u'.^^ shoulder.) 



Gymnocorymbus nemopterus sp. nov. Fig. 8. 



Head 31; depth If; D. iv, 9, i; A. iv, 32, i; P. i, 11; V. i, 7; 

 scales 33 in 1. 1. to caudal base and 2 more on latter; 10 scales above 

 1. 1.; 10 scales below 1. 1. to anal origin; 12 predorsal scales; head 

 width 1| its lengih; head depth at occiput 1; snout 4 in head, meas- 

 ured from upper jaw tip; eye 2|; maxillary 2|; interorbital 2^; 

 least depth of caudal peduncle 2; first branched anal ray 1|; pec- 

 toral 1; ventral 1|. 



Body deeply ovoid, compressed, upper anterior profile double 

 concave, and lower profile much more bulging. Body edges con- 

 stricted, though not trenchant, and greatest depth at dorsal origin. 

 Caudal peduncle well compressed, its length about half its least 

 depth. 



12 Tetragonopierus chrysargyreus Giinther, Cat. Fish. Brit. Mus., VII, 186P, 

 p. 328. Essequibo. 



