eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 457 



Head 3.75-4; depth 3; D. 7 or 8; A. 8; scales 25-27, about fourteen scales 

 in front of dorsal; eye 3 in head, 2 in interorbital; origin of dorsal equidistant from 

 base of middle caudal rays and thirteenth scale in front of the dorsal; origin of 

 anal in the female about under origin of dorsal; ventrals in the female very 

 short, half the length of the head; the outer rays of the ventral in the male pro- 

 longed, equal to head without snout, their tips reaching the tips of the posterior 

 anal rays; first anal ray a little longer than head without the snout. 



Sides with reticulations and silvery and dark cross-bands; frequently a black 

 spot on the sides in front of the vertical from the dorsal; upper and lower margins 

 of caudal black in the male. 



Acanthophacelus Eigenmann. 

 Acanthophacelus Eigenmann, Proc. U. S. Nat. Mus., XXXII, 1907, 426, fig. 1. 



Type, Pcecilia reticulata Peters. 



Each jaw with two series of teeth; intromittent organ short, with numerous 

 recurved hooks on the anterior and posterior margins. Males much smaller than 

 the females and brilliantly colored. Viviparous, females 20 mm. long being mature. 



Key to the Guiana Species of Acanthophacelus. 

 a. Male with a bright silvery lateral band, bordered above and below by black; females with wavy brown 



lines between the rows of scales on the flanks melanzonus. 



aa. Male with two to four spots of varying size and variously placed along the sides, very variable; female with 



reticulated sides, unspotted reticulatus. 



aaa. Male with a black caudal spot, usually prolonged along the dorsal and ventral margins; both male and 

 female with a dark band on the upper part of the sides; about six scales behind the head., bifurcus. 



304. Acanthophacelus melanzonus Eigenmann. (Plate LXIV, figs. 5, 6.) 

 Acanthophacelus melanzonus Eigenmann, Ann. Carnegie Mus., VI, 1909, 51; Repts. 



Princeton Univ. Exp. Patagonia, III, 1910, 548. 



Type, a male, 27 mm. Georgetown trenches. (Carnegie Museum Catalog of 

 Fishes No. 108G.) 



Cotypes, several females, the longest 39 mm. Georgetown trenches. (C. M. 

 Cat. No. 1087a-e; I. U. Cat. No. 11762.) 



Head 4+ ; depth 3.66-4; D. 6; A. 9; scales 27 to base of caudal; eye 3 in 

 head, 3 in interorbital; depth of caudal peduncle 6.5 in the length; fourteen to six- 

 teen scales in front of the dorsal; distance of origin of dorsal from caudal equal to 

 eleven scales in front of the dorsal; end of anal and origin of dorsal equidistant 

 from base of middle caudal rays; ventrals in the female barely reaching anal; 

 pectorals beyond origin of ventrals. 



