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BULLETIN OF THE BUREAU OF FISHERIES 
permit of the operation of a drag net. Three charges of dynamite produced only 
the species here described and, according to a native who was questioned, the 
stream in that vicinity contains no other fish. 
One of the large females examined had large roe, the ovary containing 30 
eggs measuring 2.25 millimeters in diameter and an equal number approximately 
half that size. The food in the 3 stomachs that were examined consisted mainly of 
unicellular a\gvR, but fragments of worms and winged insects also were present. 
This fish is known from the Pacific slope of southern Mexico and Guatemala, 
and it is now for the first time recorded from El Salvador. According to Gunther 
(1866) and subsequent authors this species also occurs in "western Ecuador," 
but this quite evidently is a mistake, for Meek (Pub., Field Mus. Nat. Hist., Zool. 
Ser., X, 1914) did not get it in Costa Rica; Meek and Hildebrand (Pub., Field 
Mus. Nat. Hist., Zool. Ser., X, 1916) did not take it in Panama; and Eigenmann 
(Memoir., Carnegie Mus., IX, 1922) does not record it in "The Fishes of Western 
South America." The specimens from El Salvador were taken in the Rio Molino, 
tributary to the Rio de Paz, near Ahuachapan. It was not found in the basins 
of the Rio Lempa and the Rio San Miguel, indicating that the species may reach 
the southermost limits of its distribution in the basin of the Rio de Paz. 
Family V. PCECILIIDyE 
The Top Minnows 
Body elongate, compressed posteriorly; head more or less depressed above; 
anal fin in the male modified, the anterior rays becoming more or less united and 
usually produced, forming an organ for the transmission of the sperms to the genital 
opening of the female; species small; viviparous. 
Many genera belonging to this family have been described by Regan, Eigen- 
mann, Henn, and recently by Hubbs, based mainly upon the minute structure of 
the modified anal fins of the males. The nimiber of genera that have been proposed, 
particularly in consideration of Hubbs's recent additions (Misc. Pub., Mus. Zool., 
Univ. Mich., No. 13, 1924, pp. 5-11), is rapidly approaching the total number of 
species recognized. Geiser (Amer. Midi. Nat., VIII, 1923, 175-188, with 18 figs.), 
in his studies of the minute structure of the modified anal fins (" Gonopod") of the 
Gambusia of the United States, which, by most recent authors, have been considered 
all identical as to species, has shown that three and possibly four divisions may be 
made. If the microscopic structure of the intromittent organ is used as a generic 
character, each species, as described and figured by Geiser (it would appear from the 
work of Hubbs, at least), should also constitute a genus. The use of the structure 
of this organ alone, as a generic character, obviously results in too many divisions, 
and the genus loses its value as a convenience in classification. 
The author is of the opinion that the intromittent organs could be grouped as 
to general type or gross structure and thus serve a useful purpose, in combination 
with other characters, in defining genera; as, for example, in Molhenesia the modified 
portion of the fin is not greatly produced and it has a membranous covering (some- 
times referred to as a hood), which covers or shields the anterior part of the organ, 
