ElGENMANN : THE EXPEDITION TO BRITISH GUIANA. 49 



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. holmicc. 



cc. Head 4.66-5 ; depth 5.5-6; D. 8 ; A. 14-16; scales 46-52 plus sev- 

 eral on the base of the caudal rays ; about 33 scales in front of dorsal ; 

 eye 3.75 in the head, 2 in the interorbital ; sides in male with alter- 

 nating light and dark stripes, the middle line of the sides light, bor- 

 dered 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. 

 bb. Anal H-13 ; head 4.5 ; depth 5.5. 



d. Scales 42 or 43 ; D. 6 or 7 ; A. 11-12 ; caudal broadly rounded ; origin 

 of anal equidistant from base of middle caudal rays and upper angle 

 of gill-openings ; base of the anal equals the head or head less snout ; 

 about 30 scales before the dorsal ; female with a faint black spot on 

 upper part of caudal peduncle ; sides of the females with a dark spot 

 on the center of each scale ; sides of the males with a dark spot on the 

 center of each scale and dark stripes between the rows of scales espe- 

 cially noticeable on the flank, the dark spots becoming obscure at times 

 with the increase in intensity of the stripes ; ventrals pale ; caudal 

 cross spotted ; spots of the upper part of the sides olive-green, those 

 of the lower rusty. stagnatus, 



dd. Scales 42 plus several on the base of the caudal peduncle. D. 7 ; A. 

 13 ; caudal pointed, lanceolate, with cross-bands between the rays ; 

 origin of the anal equidistant from the base of the middle caudal 

 rays and the second scale behind the upper margin of the pectoral ; 

 base of anal equals head less opercle ; about 3 scales before the 

 dorsal. lanceolatus. 



Rivulus breviceps sp. no v. 



Type, 50 mm. (No. 1075 Carnegie Museum Catalog of Fishes. ) 

 Shrimp Creek. 



Cotypes, 4 specimens, 50, 35, 32, and 18 mm. respectively, at least 

 the two larger, males. Shrimp Creek where the path from Tukeit to the 

 head of the Kaieteur crosses it. (C. M. Cat. No. 15 15 ; I. U. Cat. No. 



11758.) 



Distinguished by its short head, few scales and absence of longitudi- 

 nal markings. This species was taken with R. waimacui. 



