314 Fretp Museum or Natura History — Zoétocy, Vor. X. 
fin of the males. Since, with two exceptions, all the species treated of 
here belong to this subfamily, we have followed for the most part 
Mr. Regan’s classification. However, in as much as the modified anal 
fin of the males vary so essentially in different species, its use as a generic 
character seems to us to lead to too many divisions, resulting in nearly 
as many genera as species. It is, therefore, our opinion that this char- 
acter should be regarded of specific, rather than of generic importance. 
KEY TO THE GENERA. 
a. Males with the anal fin advanced and modified into an intro- 
mittent organ. Species viviparous. 
b. Ventral fins similar in both sexes. 
c. Mouth not wholly transverse, the cleft partly lateral; teeth 
conical, immovable. 
d. Distal portion of produced rays of anal fin in male directed back- 
ward, usually with one or more retrorse spines or hooks. 
Gambusia, p. 314. 
dd. Distal portion of produced rays of anal in male directed forward, 
with or without antrorse hooks. Priapichthys, p. 319. 
cc. Mouth transverse; teeth slightly compressed, movable; the 
intromittent organ long and slender, without hooks or serrations 
at apex. Peciliopsis, p. 324. 
bb. Ventral fins in the male enlarged, the second ray notably pro- 
duced; teeth in the jaws movable; the first prolonged ray of anal 
fin in male bearing a small antrorse hook at apex. 
Mollienisia, p. 326. 
aa. Anal fin in the males not modified into an intromittent organ. 
Species oviviparous. Rivulus, p. 330. 
38. Genus Gambusia Poey. 
Gambusia Poey, Memorias, I, 1855, 382 (type Gambusia punctata Poey). 
Gambusia Regan, Proc. Zool. Soc. Lond., 1913, 981. 
Body elongate, moderately compressed in the female; mouth small, 
the branches of the lower jaw firmly united; teeth fixed, conical, in 
bands, the outer ones slightly the larger; branchiostegals 6; anal fin of 
female more or less in advance of the dorsal; anal of male much ad- 
vanced, its anterior rays modified into an intromittent organ; alimentary 
canal short; vertebra about 32; viviparous. 
This genus, as restricted by Regan, includes species in which the 
modified anal of the male is about % the length of the body of the fish 
and is formed of three rays. 
