125 



Hyuorhyxchus notatus, Kaf. Blunt-nosed M.nnow. 



This extremely abundant minnow occurs in streams and rivers 

 throughout the State, but has not been found bj- us in ponds. Spe- 

 cimens were taken, however, in the small lakes of Northern Illinois. 



The intestine is aI)out two and one half times the length of the 

 head and body. The gill-rakers are few, short, and thick, being 

 about one fifth of the length of the corresponding filaments. 



Nine specimens were studied, from all parts of the State, when 

 their food proved to be so uniform in character that further obser- 

 vations were deemed unnecessary. Mud made about eighty per cent, 

 of the contents of the alimentary canal, the remainder consisting 

 of unrecognizable vegetable debris, with a few filaments of Algae. 

 Undeterminable insects occurred in one, and a single specimen of 

 Oypris in another. 



Hybognathus nuchalis, Ag. Blunt-jawed Minnow. 



This species is likewise generally distributed in rivers, creeks, and 

 ])onds, occurring in our collections from Galena to Cairo, and at a 

 great number of points intermediate. 



The alimentary canal in this genus is elongate, being about four 

 times the length of the body. The gill-rakers are few and rather 

 short, triangular in form, and about one fourth to one fifth the 

 length of their corresponding filaments. 



Eight specimens of this species were dissected, with results in all 

 respects similar to those given for the other members of this group. 

 Filamentous Algs, diatoms, and a few accidental fungus spores, 

 were the only objects found imbedded in the quantities of mud which 

 filled each intestine. 



Summary of the Group. 



If we average the results of the four species studied, belonging to 

 this first group, we shall find that about three fourths of the con- 

 tents of the stomach and intestine consist of soft, black mud, the 

 remaining fourth being derived from both animal and vegetable 

 substances, about three times as much from the latter as from the 

 former. The animal food is chiefly insects, both terrestrial and 

 aquatic, and the vegetation is divided about equally between Algas 

 and miscellaneous fragments of higher plants. This group, with 

 long intestine and grinding pharyngeals, is consequently to be con- 

 sidered as essentially limophagous. We find this peculiar form 

 of pharyngeal teeth associated only with intestines of this type. 



Group. ^_ < 



Intestines moderately long; pharyngeal teeth hooked, with grinding surface. 



Chrosomus erythroctASTer, Raf. Eed-bellied Dace. 



This species is locally abundant, although not generally common. 

 It occurs in clear streams in the northern part of the State, but 

 has not been taken by us in Central or Southern Illinois. 



