ElGENMANN : THE EXPEDITION TO BRITISH GUIANA. 51 



Cotypes, 13 males, the larger 41 mm. ; 6 females, the largest 46 mm. 

 Christianburg. (C. M. Cat. No. 1083, a-d '; I. U. Cat. No. 11 761.) 



Abundant in little pools just below the saw-mill at Christianburg. 

 Several specimens probably belonging to this species were sent me 

 from Kumaka on the Demarara above Wismar. 



Caudal spots always along the rays, rarely confluent into zigzag 

 cross-bars , anal plain or spotted, dorsal spotted. 



Rivulus lanceolatus sp. nov. 



Type unique, 42.5 mm. long. (No. 1084 Carnegie Museum Catalog 

 of Fishes. ) Rockstone. 



Rivulus frenatus sp. nov. 



Type unique, 28 mm. (No. 1085 Carnegie Museum Catalog of 

 Fishes.) Gluck Island. 



Genus Acanthophacelus Eigenmann. 



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 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. x% 



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 6 scales behind the head. bifurcus. 



Acanthophacelus melanzonus sp. nov. 



Type, a male, 27 mm. (No. 1086 Carnegie Museum Catalog of 

 Fishes. ) Georgetown Trenches. 



Cotypes, several females, the longest 39 mm. Georgetown 

 Trenches. (C. M. Cat. No. 1087, a-e ; I. U. Cat. No. 11 762.) 



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

 eye 3 in head, 3 in interorbital ; depth of caudal peduncle 6\ in the 



18 Acanthophacelus reticulatus (Peters). 



This is the most abundant of the Pceciliids found in the Georgetown trenches. I 

 am not able to distinguish it from the " millions " of Barbados. The three species of 

 Acanthophacelus together with Pcecilia vivipara Bloch & Schneider are the only species 

 in the Georgetown trenches. The latter is the largest of the Pceciliids in the George- 

 town trenches ahd can readily be distinguished by its inconspicuous alternating bands 

 of lighter and darker. The sides between the dorsal and pectoral of the female fre- 

 quently have a dark spot surrounded by silvery ; the upper and lower margins of the 

 tail in the largest males is black. 



