452 MEMOIRS OF THE CARNEGIE MUSEUM 



dd. Intromittent organ with many retrorse spines in front and behind; males highly ornamented 



and much smaller than the females Acanthophacelus. 



cc. Caudal peduncle with a knife-like ridge below; intromittent organ very long, placed under the 

 pectoral, the ventrals of the male under the gill-opening; teeth conical, in a few series. Slender, 

 hyaline. ( Tomeurinm.) Tomeurus. 



Subfamily Fundulin^e. 

 Rivulus Poey. 



Rivulus Poey, Memorias sobre la Historia Natural de Cuba, II, 1858, 307, 383. 



Type, Rivulus cylindraceus Poey. 



Dorsal smaller than anal and farther back; females more brilliantly marked 

 than the males and frequently with a caudal ocellus. 



R. waimacui showed remarkable powers of climbing the high steps in the creek 

 bed. One would spring out of the water and remain attached by its tail to the 

 side of the rock, whence it would leap to a still higher point. 



Key to the Guiana Species of Rivulus. 

 a. Sides without longitudinal markings, except a dark band from tip of lower jaw, continued as a darker 

 shade of the general color of the side; head 4; depth 4.75; D. 9 or 10; A. 12; scales 35, counting to the 

 last one on the caudal; twenty to twenty-three scales in front of the dorsal; eye 3.5, greater than snout, 

 1.6 in the interorbital; occipital scales as large as the two bordering it on its sides; caudal broad, sub- 

 truncate or rounded, with angular corners above and below; sides dusky, centers of the scales of the 

 back darker; middle of caudal with about five cross-bars; ventrals margined with dark; dorsal and anal 

 dark; origin of anal equidistant from base of middle caudal rays and upper angle of gill-opening. 



breviceps. 

 aa. Sides with longitudinal markings. 



b. Anal 14-17. 



c. Head 4-4.5; depth 5; D. 9 or 10; A. 15-17; scales 43 plus 4 on the base of the caudal rays; eye 3.5 

 in the head, equal to snout,. 1.6 in the interorbital; occipital scale very narrow; caudal broadly 

 rounded; origin of anal equidistant from base of middle caudal rays and upper angle of gill- 

 openings; about thirty scales in front of the dorsal; female with a black spot on the upper 

 part of the caudal peduncle; anterior parts of the male with numerous longitudinal lines; 

 middle series of scales on caudal peduncle and second series above and below this with series 

 of conspicuous spots; similar spots irregularly placed on other scales of the caudal peduncle 

 and forward in the male; dorsal and caudal, and in less degree, the anal profusely spotted in 



the female, less so in the male; ventrals and anal margined holmiae. 



cc. Head 4.66-5; depth 5.5-6; D. 8; A. 14-16; scales 46-52 plus several on the base of the caudal rays; 

 about thirty-three scales in front of dorsal; eye 3.75 in the head, 2 in the interorbital; sides 

 in male with alternating light and dark stripes, the middle line of the sides light, bordered 

 with rather wider dark bands, which have lighter spots or streaks in the center, above and 

 below these alternating light and dark stripes; sides in female with a median dark stripe, a 

 second one some distance below it and another above it, all much heavier on the caudal 

 peduncle, where the lower of the three becomes especially heavy; ventrals and anal margined; 

 caudal spotted near base in the female waimacui. 



