i86 Field Columbian Museum — Zoology, Vol. VII. 



abundant. I examined many large catches of the latter and did 

 not find in them a single species of Gulumina. I observed this 

 small fish to be exceedingly abundant along the railroad fill. 

 During warm days, when the sun was shining brightly, they would 

 rise in large schools near the surface of the water. On coming 

 near the water's edge, or approaching them slowly in a boat, they 

 would sink to a considerable depth and hide among the rocks. The 

 food of this fish consists almost entirely of insects and insect 

 larvae. It is said to spawn about March and April. Lakes Amati- 

 tlan and Atitlan. scarce. 



Poecilia sphenops C. & V. Pescadito. 



There are probably more individuals of this fish in Lake 

 Amatitlan than of all other fishes combined. It is a small fish, 

 in shape and size much like the Gulumina. This fish is vivi- 

 parous ; that is, it brings forth its young alive. Each female has 

 a brood of from 30 to 50 small fishes. The young are born in 

 March and April and May. This fish feeds on filamentous algae, 

 the larger species of free algae, and the tender parts of the Chara, 

 Potamogeton and Ceratophyllum. They also eat mud in which 

 microscopic animal and plant life is abundant, and also insects and 

 insect larvae when these are abundant. This species comes near 

 shore in greater numbers during the night, yet they seem very 

 plentiful in daytime in shallow water. They are caught in large 

 quantities by the residents of this region. Their flesh is quite 

 firm and well flavored, but the many small bones and their small 

 size prevent them from being very desirable for food. The 

 absence of better fish, or the presence of no fish at all, and the 

 ease with which they can be taken in large numbers, largely 

 explains why so many are used for food by residents about the 

 lakes. These fishes are captured by the small-mesh throw-nets 

 used so extensively in Spanish American countries. In order to 

 make their capture more certain and easy, the fishermen build 

 nearly circular basins along the margins of the lake. These 

 basins are formed by placing rocks around the margin, enclosing 

 areas of shallow water usually about one or two feet deep and 

 from 5 to 15 or 20 feet in diameter. These are often built in the 

 shade of an overhanging bush, or they may or may not be covered 

 with brush. On the side towards the lake a narrow opening is 

 left through which these small fishes enter the basin, in u short 

 time the Pescaditos enter these basins in large numl)ers. After 



