FISHES OF EL SALVADOR 
255 
but which is distally free. In Gambusia, on tJie other hand, the intromittent organ 
is notably produced and the membranous hood is wanting. The characters of the 
intromittent organ in these genera are supported by the comparatively long, con- 
voluted intestine in Mollienesia, while Gambusia has a short intestine, which is not 
convoluted. The minute structure of the intromittent organ would then become 
of specific value only, and it is believed that less confusion would result than by 
retaining 'and adding to the already too numerous very closely related "genera." 
Some of the species of this family — as, for example, the Gambusia of the United 
States — have been found to be of great value as eradicators of mosquito larva?. 
Limited observations made in the field, as well as the examination of stomach 
contents, indicate that all the species of this family occurring in El Salvador are of 
value as destroyers of mosquitoes. 
KEY TO THE GENERA 
a. Intestinal canal longer than the total length of the body, usually more or less convoluted; 
dorsal fin in adult male very high; the intromittent organ not much produced, shorter than 
head, anteriorly shielded by a short membranous hoodL Mollienesia, p. 255. 
aa. Intestinal canal not longer than the length of body and not convoluted; dorsal tin in males 
not much, if any higher than in females; the intromittent organ greatly produced, longer 
than head, and without a membranous hood Priapichthys, p. 258. 
7. Genus MOLLIENESIA Le Sueur 
Mollienesia Le Sueur, Jour., Ac. Nat. Sci., Phila., II, 1821, 3 (type Mollienesia latipinna Le Sueur). 
Body elongate, rather robust; head more or less depressed; mouth transverse; 
teeth in the jaws in bands, the outer ones movable; dorsal fin elongate in the adult 
male, much higher than in the female; intromittent organ short, not as long as 
head, anteriorly shielded by a membranous hood; intestinal canal convoluted and 
longer than the total length of the fish. A single variable and rather widely dis- 
tributed species was taken in the waters of El Salvador. 
7. Mollienesia sphenops (Cuvier and Valenciennes) 
Chimbola 
Poicilia sphenops Cuvier and Valencieunes, Hist. Nat. Poiss., XVIII, 1846, 130, PI. DXXVI, fig. 2 (Vera Cruz, Mexico); Regan, 
Biol. Cent. Amer., Pisces, 1907, 102, PI. XIII, figs. 1-7. 
XiphophoTUS gilli Kner and Steindachner, Abiaandl. l£. Bayer, Ak. Wiss. Miinchen, X, 1864, 25, PI. IV, fig, 1 (Rio Chiagres, 
Panama). 
Platypadlus mentalis Gill, Proc, Ac. Nat. Sci., Phila., 1876, 335 (Panama). 
Padlia boucardi Steindachner, Sitzb. k. Ak. Wiss., Wien, LXXVI, 1878, 386, PI. Ill, fig. 263 (Colon, Panama). 
Posdlia salvatoris Regan, Ann. and Mag, Nat. Hist., 7 ser., XIX, 1907, 65, and Biol. Cent. Amer., Pisces, 1907, 104, PI. XIV, 
figs. 2 and 3 ("Salvador"). 
Platypadlus tropicus Meek, Pub,, Field Col, Mas,, Zool, Ser,, VII, 1907, 146 (Turrialba, Costa Rica). 
Poedlia tenuis VLtfsK Pub,, Field Col, Mus., Zobl, Ser,, VII, 1907, 147 (Tiribi; San Jose and Rio Maria Aguilar, Costa Rica). 
Mollienesia sphenops tropica Meek, Pub,, Field Mus. Nat, Hist., Zool. Ser., X, 1914, 116 (Costa Rica). 
Head 3 to 4.25; depth 2.75 to 3.65; D. 9 to 11 ; A. 8 to 10; scales 25 to 29. 
Body rather robust, variable, compressed; caudal peduncle strongly compressed, 
its depth 1.1 to 1.85 in head; head depressed, flat above, broader than deep over 
middle of eyes; snout broad, its length 2.8 to 3.6 in head; eye 3 to 4.4; interorbital 
1.65 to 2.35; mouth transverse, directed slightly upward; lower jaw a little the 
longer; teeth in bands, the outer ones movable, enlarged, slightly broadened, curved 
