DEC. 28, 1916. FISHES OF PANAMA MEEK AND HILDEBRAND. 315 



"The distal segments of the first prolonged ray are produced into processes 

 directed more or less towards its apex; the anterior branch of the second prolonged 

 ray is slender distally and at some distance from the end has an antrorse projection 

 which may be termed the ' elbow' ; the posterior branch of this ray ends in a retrorse 

 pointed hook or barb, and the segments immediately proximal to the elbow of the 

 anterior branch are produced backwards into serrse; the third prolonged ray ends 

 in a hook more or less similar to that of the second." (Regan) 



The males of this genus and related genera are smaller than the 

 females, and more elongate; they are apparently fewer in number. All 

 Gambusia are small, and as a net sufficiently small to capture females will 

 permit the males to pass through it, the few males taken by the 

 collector may not indicate their true ratio. Many of the species of this 

 genus live in swamps and lowland streams, but a few species throughout 

 Mexico and Central America are found in clear mountain streams at as 

 high an altitude as any fishes are found. Gambusia feed chiefly on 

 insects and small Crustacea. To some of the species are credited the 

 eating of mosquito larvae. 



We here tentatively refer to this genus 2 species, G. episcopi 

 and G. cascajalensis, that do not have any definite retrorse hooks 

 on the distal portion of the intromittent organ, but they agree in 

 other respects with this genus. 



KEY TO THE SPECIES. 



a. Intromittent organ of male with 2 strong retrorse hooks at apex, 

 and anteriorly with strong serrations; each scale with a dark dot, 

 forming lines along the rows of scales; dorsal and caudal with 

 black spots, forming bars. nicaraguensis, p. 316. 



aa. Intromittent organ of male without retrorse hooks or strong 

 serrations at apex; no dark lines along the rows of scales; anal 

 fin with a black spot at base, which may or may not be extended 

 to tip of rays. 



b. Body rather robust, the depth 3.2 to 4.1 in length; caudal ped- 

 uncle 1.15 to 1.6 in head; origin of dorsal in female over or 

 slightly anterior to vertical from middle of anal; anal fin not 

 falcate; skin underneath the scales strongly pigmented, mark- 

 ing the margins of the scales; sides with more or less distinct 

 dark spots or bars. Largest females 52 mm. in length. 



episcopi, p. 317. 



bb. Body slender, the depth 3.7 to 4.5 in length; caudal peduncle 1.7 

 to 2 in head; origin of dorsal in female over posterior rays of 

 anal; anal more or less falcate; the rows of scales very indis- 

 tinctly marked; sides without spots or bars. Largest female 62 

 mm. in length. cascajalensis, p. 318. 



