112 Annals of the Carnegie Museum. 



3.5 in head, 1.5 in interorbital and equal to the snout. D. 7; A. 14; 

 42 scales in horizontal series, 8 between dorsal and anal. 



Head broader than deep. Very much compressed posteriorly, 

 greatly depressed anteriorly, width of fish at ventrals one-half its 

 width at the occiput. Profile slightly arched, cleft of mouth hori- 

 zontal. 



Origin of dorsal three times as distant from the tip of the snout as 

 from the base of the caudal, inserted over the last anal ray. Origin of 

 anal equidistant from operculum and base of caudal, ventrals equi- 

 distant from tip of snout and base of caudal, one and one-half as long 

 as eye. 



Coloration olivaceous, a narrow brown stripe between the rows of 

 scales. Top of head and dorsal ridge darker. 



10. Rivulus brevis Regan. 

 Rivulus brevis Regan, Ann. Mag. Nat. Hist., (8), X, 1912, p. 504 (Colombia). 



University of Michigan, ten specimens, 26-45 mm., from Fundacion, 

 near Santa Marta, Dept. of the Magdalena, Colombia. , 



Much deeper and more compressed than most of the species of this 

 genus. Head deeper than broad in mature examples; in young, as 

 broad as deep. 



Head 3.3-3.5; depth at origin of ventrals 3.5-3.8; depth of caudal 

 peduncle 5.5-6 in length and 1.6 in head. Eye 3 in head, slightly 

 less than interorbital. Width of the head 1.5 in the depth, which is 

 1.5 in the length. D. 8-9; A. 12-13; scales 29-30 in a lateral series, 

 8 or 9 in transverse series. 



Origin of dorsal twice as distant from the anterior margin of the 

 orbit as from the base of the caudal. Dorsal rises over the middle of 

 the anal. In adult specimens the rays of all the fins are prolonged. 

 The eighth to the eleventh rays of the anal are extended to form a 

 streamer, which reaches to the base of the lower caudal fulcrum. 

 Dorsal rays also prolonged. Middle rays of pectoral prolonged and 

 reaching almost to middle of ventrals, which are extended on to the 

 base of the anal. Caudal rays elongated, lowest rays often forming a 

 streamer, basal third with a heavy sheath of small scales. All fins 

 blackish. 



Genus Gambusia Poey. 

 Gambusia Poky, Memorias de Cuba, I, 1855, p. 382; Regan, Proc. Zool. See. 



London, 1913, p. 981. 



