70 The- Food of tlie Smaller Fresh- Water Fishes. 



teetli, while the throat is destitute t)f 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 larva? 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 

 jndex, retrocurva and liyalliia., ^^imocephalus americanus., Bosmi- 

 na, Chydorus, Pleuroxus, Alona, and Eurycercus; and among the 

 Copepoda were Cyclops thomas^ Canthocamptus, Diaptomus, 

 Limnocalanus, and Epischura lacustris. Spiders and terres- 

 trial insects, accidentally washed or fallen into the water (the 

 latter including Chalcididre, various Diptera, plant-lice, Tettigoni- 

 d£e, Thrips, and Podura), amounted to twelve per cent, of the food. 

 The only peculiarities of food corresponding to diiferences of local- 

 ity were found among the group from the northern lakes, in which 

 the Chironomus larv<e were present in diminished ratios, while 

 the Cladocera were more abundant. 



FAMILY CYPRINODONTID^. 



This family consists, in Illinois, of four species, one of Fundu- 

 lus and three of Zygonectes.* The family is divided into two 

 sections, carnworous and herbivorous, by Dr. Giinther in his "In- 



■•■■I do not consider Fundulus menona, Jor. and Cope., as distinct. 



