129 



by only one of the specimens. Insects, eaten by nineteen, were 

 reckoned at forty-five per cent., only one fourth of them terrestrial. 

 Oyrinid larvie, Corixa, and larvffi of Palingenia hiliveata were among 

 the forms recognized. The crustacean ratio was insignificant, stand- 

 ing at only three per cent., all the abundant amphipod,' AUorchcstes 

 dentata, with the exception of traces of a considerable variety of 

 Entomostraca, including Chydorus, Acropcrns leacocephcduH, and 

 Cypris. One of the water-worms (Lumbriculus) was noticed in a 

 single specimen. Vegetable food was reckoned at thirty-eight per 

 cent., only about one third of it consisting of Algae, and the rest of 

 accidental fragments, including the seeds, anthers, and pollen of 

 plants, with a little Potaniogeton and various forms of fungus 

 spores. One of the commonest of the Algie was Cladophora glome- 

 rata* taken by those from Effingham. The fact has already been 

 noticed that one of the specimens had eaten only fishes. Five had 

 confined themselves to an insect diet, while twelve had derived more 

 than half their food from the vegetable kingdom, one of them eating 

 ninety- five per cent, and another one hundred. 



Hemitremia. heterodox, Cope. Northern Hemitremia. 



This species, extremely abundant in Northern Illinois, has not 

 been taken by us south of the central part of the State, North of 

 Eock River it has been generally found in streams and lakes of all 

 descriptions, from Lake Michigan down. 



The gill-rakers are few in number, but thick, triangular, and 

 rather long, those on the posterior part of the arch being from a 

 fourth to a third the length of the filaments. The intestine is con- 

 tained one and one fourth times in the length of the head and body. 



Eighteen specimens were studied, suitably distributed as to time 

 and place. A little mud was found in the stomach of one. Only 

 about one tenth of the food consisted of vegetation, chiefly flowers 

 and seeds. Traces of filamentous Algae occurred in two of the 

 specimens. Univalve MoUusca were noticed in one, and insects in 

 twelve, amounting to more than a fourth of the entire food. These 

 w-ere chiefly larvae of Chironomus (twenty per cent.), ephemerid 

 larvie occurring in but one. Crustacea were reckoned at fifty-eight 

 per cent., all Entomostraca, with the exception of a single AUorcJtes- 

 tes (lentata. About two thirds of these were Cladocera, the remain- 

 der being Ostracoda and Copepoda. Rotifers and Protozoa also 

 rarely occurred, the latter including Centropyxis and Dilfiugia, Five 

 of the specimens had eaten Entomostraca only, and two others ninety 

 per cent, or more. Only two had derived more than half their food 

 from vegetable sources. 



It will be seen that the peculiar fact with respect to this species, 

 was the large per cent, of Entomostraca appropriated. I find nothing 

 in the structure of the fish to explain this circumstance, other than 

 the somewhat unusual development of the gill-rakers and the small 

 size of the species. The latter probably had more to do with it 



*Kindlv di-tormined for me l>v Rev. Fraiieis Wolli-. P.t'thli'lieni. Pa. 



F. C.-i) 



