OYPRINODONT FISHES. 981 



First prolonged ray without aiiti'orse spine ; last without 



terminal process 23. PceciUa. 



First prolonged ray without antrorse spine ; end of last 

 bearing a pair of processes directed outwards and 



towards the base of the tin 24:. Lehistes. 



First prolonged ray bearing a small antrorse spine at or 



near its end; last with processes as in Lelistes 25. Mollienisia. 



fi. First prolonged ray becoming abruptlj' 

 slender at some distance from end, not 

 sharply serrated, bearing a small antrorse 

 spine at or near its end ; last prolonged 

 ray without terminal processes 26. Limia. 



1. Alfaro Meek, 1912. 



Petalosoma (non Lewis) Regan, Ann. Mag. Nat. Hi.st. (8) ii, 

 1908, p. 462. 



Alfaro Meek, Field Mas. Publ. Zool. x., Sept. 1912, p. 72. 



Petalurichthys Regan, Ann. Mag. Nat. Hist. (8) x., Nov. 1912, 

 p. 494. 



This genus resembles Gambusia, except for the sharp lower edge 

 of the tail. The intromittent organ (text-fig. 169 F, p. 990) is 

 simple in structure, and the pelvic fins are enlarged in the male. 



1. Alfaro cultratus. 



Petalosoma cultratimi Regan, Ann. Mag. Nat. Hist. (8) ii. 

 1908, p. 462, 



Alfaro acutiventralis Meek, Field Mus. Publ., Zool. x. 1912, p. 72, 



Depth 3| in the length. Dorsal 7-8 ; when laid back nearly 

 reaching caudal. Anal 9-10, in advance of dorsal. 32 to 35 

 scales in a longitudinal series. Total length 45 to 90 mm. 



Costa Rica. 



2. Alfaro amazonum. 



Petalosoma amazonum Regan, Ann. Mag. Nat. Hist. (8) viii. 

 1911, p. 659, figs. 



Depth 3|^ in the length. Dorsal 8-9, when laid back not 

 reaching caudal., Anal 10, in advance of doi-sal. 33 or 34 scales 

 in a longitudinal series. Total length 35 to 51 mm. 



R. Amazon at Obidos. 



2, ToMEURUS Eigenm., 1909. 

 Ann. Carnegie Mus. vi. p. 53. 



ToMEURUS GRACILIS. 



Eigenm. L c. and Mem. Carnegie Mus. v. 1912, p. 460, pi. Ixv. 

 figs. 7-8. 



British Guiana. 



3. Gambusia Poey, 1855 *. 

 Mem. i. p. 382. 

 Gambusia (pai't.) Glinth. Cat. Fish. vi. p. 333 (1866) ; Garman, 



* G. picturata Poey (' Synopsis,' p. 410, 1868) is a doubtful species of uncertain 

 position. 



