ElGENMANN : THE EXPEDITION TO BRITISH GUIANA. 53 



Male with the general color of the female, the dorsal nearly black ; 

 caudal with a variously shaped dark olive-green vertical band at its base, 

 usually continued into a long prong along the entire upper margin of 

 the fin, very frequently continued into a shorter prong along the ven- 

 tral edge of the fin ; the basal bar sometimes diffused over the entire 

 caudal peduncle ; anal with some black. 



In life sides of male yellowish, caudal peduncle pokeberry-red to 

 dark olive-green ; upper caudal prong bordered by pokeberry-red be- 

 low, or rusty ; one male with a black streak and a milk-white margin 



to the anal. 



Tomeurus gen. no v. 



Teeth conical, in about three series ; dorsal placed far back over 

 the last fourth of the body ; anal in the female in advance of the middle 

 of the body, in the male moved forward to below the origin of the 

 pectorals ; ventrals not evident in the female, minute, under the 

 upper angle of the gill-opening in the male ; pectorals large ; alimen- 

 tary canal much shorter than the body ; caudal peduncle with a ven- 

 tral knife-like ridge extending almost its entire length, resembling an 

 adipose fin, but composed of about sixteen paired scales ; intromittent 

 organ of the male very long, composed of the first three anal rays, the 

 first divided into two lateral prongs near the tip, each of which has a 

 backward projecting process near its middle and a slender spine-bearing 

 appendage near its base, a similar but larger spine -bearing appendage 

 between the bases of the prongs. 



Tomeurus gracilis sp. no v. 



Type, 31 mm. (No. 1093 Carnegie Museum Catalog of Fishes. ) 



Cotypes, 3 d\ 29-30 mm. Mud Creek in Aruka River. 



Cotypes, 3 9, about 20, 24 and 28 mm. Mud Creek in Aruka 

 River. (C. M. Cat. No. 1094; I. U. Cat. No. n 767.) 



Cotypes, 1 ?, 18 mm. Wismar. (C. M. Cat. No. 1095.) 



This species represents the type of a new subfamily of Pceciliids. 



Head 5.5 ; depth 6.5 ; D. 6 ; A. 6 ; scales 39 from occiput to tail ; 

 7 between the middorsal scale and the ventral ridge ; 26 scales in front 

 of the dorsal ; eye longer than snout, 2J in head, a little less than 

 the interorbital. 



Very long and slender, mouth rather large, vertical, its width equal 

 to the diameter of the eye ; origin of dorsal near beginning of the 

 third fourth of the length, its height equals length of head less oper- 



