458 Mr. C. T. Regan on 



I the length of head. Caudal subtruncate. Least depth of 

 caudal peduncle § the length of liead. Scales with dark 

 edges ; a series of short dark vertical bars along the middle 

 of the side; dorsal fin with 2 or 3 series of dark spots. 



Volcano of Tenorio and Rio Grande de Terraba. 



Nine s])ecimens, 40 to 50 mm. in total length. 



Allied to G. episcojn, Steind., Q . annectens, Regan, and 

 G. tevixtbensis, Regan, differing from the two first-named 

 especially in the more posterior position of the anal fin, and 

 from the last in the fewer dorsal fin-rays. 



Petalosoma, gen. nov. 



Differs from Gamhusia in having the lower surface of the 

 tail, behind the anal fin, compressed to a sharp edge. 



7. Petalosoma cultratum, sp. n. 



Body strongly compressed, its depth 3i in the length, 

 length of head 4. Snout nearly as long as eye, the diameter 

 of which is 3 in the length of head and a little less than the 

 interorbital width. 35 scales in a longitudinal series. 

 Dorsal 8 ; origin equidistant from eye and posterior edge of 

 caudal fin. Anal 9, far in advance of the dorsal; first 

 branched ray the longest. Pectoral shorter than the head ; 

 pelvics inserted below the middle of pectoral and extending 

 to the anal. Olivaceous ; a dark linear lateral stripe on the 

 posterior part of the body. 



Rio Iroquois. 



A single specimen (J), 50 mm. in total length. 



8. Poecilia sphenops, Cuv. & Val. 

 Volcano of Tenorio. 



9. Poscilia retropinna, sp. n. 



Depth of body 3|- in the length, length of head 4-^. Snout 

 as long as eye, the diameter of which is Sj in the length of 

 head. Interorbital width equal to the distance from middle 

 of eye to free edge of operculum. 30 scales in a longitudinal 

 series. Dorsal 9 ; origin equidistant from anterior part of 

 eye and posterior edge of caudal fin ; free edge straight, the 

 first branched ray the longest. Anal 10; origin a little in 

 advance of that of the dorsal. Pectoral nearly as long as 

 the head, extending to the base of the pelvics. Caudal 

 rounded. Least depth of caudal peduncle f the length of 

 head. Olivaceous; scales with darker edges; fins pale. 



