120 

 Zygonectes inurup, Jor. and Gilb. Black-eyed Top Minsow. 



Zygonectks dispar, Ag. Striped Top Minnow. 



The first of these species is peculiar in this State, as far as known, 

 to Southern Illinois, not having l>6en taken by us north of White 

 county. The second ranges throughout. 



Six specimens of the first and two of the second were studied. 

 The food characters presented do not differ sufficiently from those 

 of Zygonectes notatus to make it worth while to treat them sepa- 

 rately, and a summary for the genus will be given instead. 



Four fifths of the food of the genus consisted of animal matter, 

 nearly one quarter being Mollusca, including Physa. Planorbis, and 

 Valvata sinrera. iHsects made less than half, and nearly half of 

 these were of terrestrial origin. Chironomus larvse, usually so abund- 

 ant in the food of insectivorous minnows, occurred here in only 

 trivial quantity. Specimens of Philhydrus were eaten by three of 

 the fishes. Corixa alternata amounted to five per cent, of their 

 food, Agrion larvae and case Morms (Leptoceridte) to two per cent. 

 Crustaceans were only four per cent, of the whole, partly x\mphip- 

 oda, but chiefly Entomostraca. The vegetable food (sixteen per 

 cent.) was chiefly Wolffia, taken by five of the specimens from 

 southern lakes. Ten individuals had, however, eaten filamentous 

 Algpe. 



Summary. 



The only essential difference between these two genera exhibited 

 by the specimens studied, is the much larger ratios of terrestrial 

 insects captured by Zygonectes, this genus eating nearly twice as 

 many as the other. This fact is possibly related to the surface- 

 swimmitig habit already mentioned, but is more likely due to the 

 smaller bodies of water in which the top minnows occur. Concern- 

 ing the food of the family as a whole, the salient characters are the 

 presence of a considerable quantity of vegetable food, (about twenty 

 per cent.) the occurrence of fifteen per cent, of Mollusca, the insig- 

 niticant quantity of Crustacea eaten (four per cent.), and the impor- 

 tance of terrestrial insects as a source of support. 



Family UMBRIMD.E. 



Umbra LiMi, Kirt. Mud Minnow. 



This species, the only one of its family in Illinois, is very abund- 

 ant in muddy ponds and ditches, and has been collected by us from 

 Lake to Union Coinily. 



The intestine is short, less than the liody in length ; the gill- 

 rakers are thick and rather long, about one luilf the length of the 

 filaments, and the pharyngeal apparatus is wholly insignificant. . 



Ten specimens were studied, from six localities, all from Southern 

 Illinois but one, which w;«s taken in C.ilumet River. V'egetable food 

 amounted to foity per cent., chieMy Wolfh i, eaten by- seven of the 



