70 
The Food of the Smaller Fresh- Water Fishes. 
teeth, while the throat is destitute of special pharyngeal appara- 
tus. The gill-rakers are unusually well developed, being numer- 
ous, slender, finely toothed, and longer than the corresponding 
filaments of the gills. Taking into account the small size of the 
fish, and the consequently small diameter of the apertures of the 
mouth and gills, it will be seen that it is provided with an espe- 
cially effective straining apparatus. The intestine is unusually 
short, the entire alimentary canal measuring considerably less than 
the length of the body without the head. 
The following account of its food is derived from the dissection 
of twenty-five specimens, obtained from Crystal Lake, Fox River, 
and Calumet River in Northern Illinois, from Peoria and Mack- 
inaw Creek in the central part of the State, and from Little Fox 
River in the Wabash Valley. The food of these specimens was 
purely animal, a little over half consisting of insects, and a little 
less than half of crustaceans. The larvae of Chironomus were 
among the most important elements of the food, standing at thirty 
per cent, of the whole. The crustaceans were all Entomostraca, 
and represented a great variety of both Copepoda and Cladocera, 
although none of the specimens examined happened to have eaten 
Ostracoda. Among the Cladocera recognized were Daphnia 
pul ex, retrocurva and hyalina , Simocephalus americanus , Bosmi- 
na, Chydorus, Pleuroxus, Alona, and Eurycercus; and among the 
Copepoda were Cyclops thomasi , Canthocamptus, Diaptomus, 
Limnocalanus, and Epischura lacustris. Spiders and terres- 
trial insects, accidentally washed or fallen into the water (the 
latter including Chalcididae, various Diptera, plant-lice, Tettigoni- 
dae, Thrips, and Podura), amounted to twelve per cent, of the food. 
The only peculiarities of food corresponding to differences of local- 
ity were found among the group from the northern lakes, in which 
the Chironomus larvae were present in diminished ratios, while 
the Cladocera were more abundant. 
FAMILY CYPRINODONTIDAL 
This family consists, in Illinois, of four species, one of Fundu- 
lus and three of Zygonectes.* The family is divided into two 
sections, carnivorous and herbivorous , by Dr. Gunther in his “In- 
*1 do not consider Fundulus menona , Jor. and Cope., as distinct. 
