FISHES OF EL SALVADOR 
259 
specimens, reaching past origin of anal in males; pectoral fins moderate, 1 to 1.85 
in head; vertebrae about 15 + 17; alimentary canal about as long as the body; peri- 
toneum black. 
Color of the sexes similar; olivaceous above; lower part of sides silvery; median 
line of sides with a row of round black spots scarcely as large as pupil, varying in 
number from 3 to 10, present even in the mature embryo (wanting only on a single 
large female) ; a faint dark vertebral band ; a sharp dark median line from anal to 
caudal: base of anal sometimes surrounded by black in large females; fins all un- 
spotted; dorsal, caudal, and anal olivaceous; other fins plain translucent. 
Many specimens of this species, ranging in length from 10 to 85 millimeters, 
were preserved. This fish inhabits both lakes and streams, but it was not taken in 
the tributaries of the Rio de Paz nor in Lakes Chalchuapa, Ahuachapan, Coatepeque, 
Chanmico, and Ilopango. Neither was it obtained in the Rio Lempa at San Marcos, 
notwithstanding that the species appeared to be common in that stream about 200 
kilometers further upstream at the village of Suchitoto. 
This fish appears to grow much larger in some localities than in others. In 
Lake Zapotitan, for example, the largest male and female obtained were, respec- 
tively, 20 and 27 millimeters in length, yet fully mature, as shown by the com- 
pletely developed intromittent organ of the male and by the presence of large 
embryos in the ovaries of the female. Specimens of this size from some of the other 
localities at which collections were made are clearly sexually immature. The 
largest fish seen, ranging a little more than 80 millimeters in length, were taken in 
the Rio San Miguel at San Miguel. The males are much smaller than the female 
and they occurred rather sparingly in the catches made. 
Many of the specimens in the collection (taken during January and February) 
are in spawning condition, the ovary usually containing large eggs in two distinct 
stages of development, in addition to smaller ova. An ovary taken from a specimen 
67 millimeters long, for example, contained 26 well-developed embryos and 30 
apparently fully mature eggs, measuring about 1.5 millimeters in diameter, and 
minute ova. The young fish when born is from 8 to 10 millimeters long, and well 
developed. The body is covered ynih dark punctulations, which usually are con- 
centrated in about three places on the median line of the sides, later forming the 
dark lateral spots which are characteristic of the species. 
Stomachs examined contained insects, fragments of fresh-water sponge, algjE, 
leaf fragments, small ova (probably insect eggs), and inorganic matter consisting 
largelj^ of sand. Field observations would indicate that the species probably is of 
considerable value as an eradicator of mosquito larvse. 
The specimens were obtained at the following localities: Lake Guija, Rio del 
Desague at Lake Guija, Lake Metapan, Lake Zapotitan, Rio Sucio at Sitio del 
Nino, Rio Acelhuate at San Salvador, Rio Lempa at Suchitoto, Rio San Miguel at 
San Miguel, and Lake Olomega. 
