ElGENMANN : THE EXPEDITION TO BRITISH GUIANA. 35 



Scales cycloid, regularly imbricate, no interpolated scales. No 

 scales on the anal, those along the base forming a sheath. Caudal 

 naked. A very minute axillary scale. 



Back dusky, margined by a darker stripe from above eye to upper 

 caudal lobe. A light band from upper part of eye, becoming widest 

 under the middle to end of dorsal in the J\ widest on caudal 

 peduncle, contracted on caudal fin in the 9. A dark band from eye 

 to upper part of gill-opening, thence descending to meet its fellow 

 on the lower surface and edge of caudal peduncle, thence curved 

 up on the caudal to tips of its middle rays ; this band more intense, 

 jagged, and more strongly decurved in the male than in the female. 

 Sides of caudal peduncle with a rusty spot on each scale ( 9 ) ; dorsal 

 in both sexes nearly uniform, darkest in the male. Upper margin of 

 caudal geranium-red, most intense in the male, below which is a con- 

 tinuation of the upper dark band of the sides, fading out toward tip 

 of upper lobe and with oval hyaline spots ; a wedge-shaped area at 

 middle of caudal and all but the base of some of the rays of vthe lower 

 lobe hyaline. Tip of anal in male scarlet, below which is a broad 

 dark band ; base and last rays hyaline. Last rays of anal ( 9 ) hya- 

 line, otherwise dark with conspicuous round or oval hyaline spots. 

 Ventrals slightly dusky. Pectorals hyaline. 



Subfamily Nannostomatin^e. 



The Nannostomatinse are minute fishes resembling Zygonectes and 

 the North American darters. 



The genera of the subfamily are distinguished as follows : 



a. A triangular occipital process; a small, circular occipital fontanel. Adipose fin 

 well developed. 



b. Lateral line complete ; teeth usually 3-pronged. Characidium, Reinhardt I. 

 bb. Lateral line incomplete ; teeth conical. Microcharax xx Eigenmann 2. 



aa. Skull truncate ; no occipital process ; no fontanel ; teeth usually incisor-like, 

 notched at tips. No lateral line. 



c. No adipose fin. 



d. Five or six scales in a transverse series ; 20-28 in a median-lateral series ; 

 jaws equal ; teeth broad at top, with five equal points. Nannostomus 12 Giinther 3. 

 cc. Adipose fin well developed ; scales five in a transverse series. 



• n Type Nannostomus lateralis Boulenger. 



12 As here understood the genus Nannostomus consists of N. beckfordii Giinther, 

 the new species described in this paper, and Nannostomus anomolum Steindachner. 



