Freshwater Fishes from Costa Bica. 459 



Boruca. 



A single specimen ( $ ) 77 mm. in total length. 



Closely allied to P. elongata, in which the origin of the 

 dorsal fin is equidistant from the end of the snout and the 

 posterior edge of the caudal, or nearer the former, the pectoral 

 extends to above the middle of the pelvics, and the interorbital 

 width is not more than the distance from the [)Osterior margin 

 of the pupil to the free edge of the operculum. 



10. Poecilia tropica, Meek. 



Depth of body 2i to 3^ in the length, length of head 3| 

 to 4^. Snout shorter than eye, the diameter of which is 

 2| to 3 in the length of head. Interorbital width equal to the 

 distance from middle of eye to free edge of operculum. 26 to 

 29 scales in a longitudinal series. Dorsal 9-10; origin equi- 

 distant from end of snout and middle (?) or basal part ( c? ) 

 of caudal fin ; first branched ray (?) or posterior rays ( ^ ) 

 the longest, the tin elevated in the male. Anal 9-10 ; origin 

 a little behind that of the dorsal ; first branched ray the 

 longest. Pectoral as long as the head, extending nearly to 

 the middle of the pelvics ( ? ). Caudal subtruncate. Least 

 depth of caudal peduncle | (?) to | ( c? ) the length of head. 

 Olivaceous ; dorsal with black spots, the basal half of the fin 

 sometimes uniformly blackish ; caudal with or without small 

 blackish spots ; sometimes a blackish blotch at the base of 

 the caudal fin. 



Rio Iroquois. 



Six specimens, 60 to 100 mm. in total length. 



This species differs from P. sphenops and agrees with 

 P. salvatoris in the shape of the dorsal fin ; it differs from 

 the latter in the larger eye. 



The synopsis of the Central American species of Poecilia 

 given in the ' Biologia Centrali- Americana ' may be modified 

 as follows, in order to include the species since described * : — 



I. Origin of anal in advance of that of the dorsal. 



A. Anal 7. 26 scales in a longitudinal series. [186G. 



1. spiluriis, Giinth., 



B. Anal 8-11. 



1. Dorsal rounded, the middle rays the longest; 27 to 30 scales 



in a longitudinal series 2. occidentalis, Baird & 



[Girard, 1853. 



* This synopsis is based on female specimens only ; in some species 

 tlie males have not yet been described. They differ from the females in 

 having the anal fin advanced and moditied into an intromittent organ, 

 whilst the dorsal is a little further forward, more or less elevated, and 

 often differently shaped. 



