525 



mens of the bivalve mollusk Sphccrimn, found in a somewhat sandy 

 deposit two hundred yards below the Ottawa wagon-bridge. The 

 characteristic foul-water organisms, Sphcerotilus, Carchesiiim, etc., 

 although common in weeds along the edges of the stream, and ob- 

 tained also from the current, were less abundant than at Marseilles. 

 The same blue-green and filamentous green algae found at Marseilles 

 were collected here also. There were no sponges, hydroids, or pla- 

 narians ; but leeches occurred now in fourteen collections. Cyclops 

 was found among the marginal algse, as above, and a single isopod 

 crustacean, Ascllus, was taken in the drift on the south shore. 



The lessening of contaminate conditions was especially shown by 

 the occurrence of small numbers of various insect larvae, including 

 those of dragon-flies, caddis-flies, and May-flies (Cccnis and He.va- 

 genia), and pupae of the sand-fly (SinmUum). Larvae and pupae of 

 Chironouuis were obtained in twenty-two collections. Diligent use 

 of the crow-foot dredge in various situations brought to light no 

 living mussels except on a bar in Fox River water just outside the 

 mouth of that stream. Here two species were obtained alive — 

 Lampsilis vcntricosa and L. Icevissinia — and dead shells of eight other 

 species. One large specimen of Anodonta corpulenta had quite re- 

 cently succumbed, the flesh being not yet decayed. 



Species of univalve mollusks, taken largely by the Ekmann dredge 

 from the bottom of the main stream, became at this point rather too 

 numerous for special mention in a preliminary report. Planorbis 

 trivohis and Physa gyrina were the most abundant, and a species of 

 Amnicola next. The number of dead shells of both Unios and uni- 

 valves, as compared with the living specimens found, was indicative 

 of an environment still difficult for mollusks. 



Our fish collections at Ottawa were made August 26 and 27, 

 191 2, with small seines and dynamite. They aggregated one hundred 

 and twenty-five specimens, representing seventeen species, of which 

 forty-six specimens belonging to fourteen species were from Fox 

 River water just outside the mouth of that stream. From the water 

 of the Illinois itself, we have the following six species: i carp, 

 I black bullhead, i red-horse, 2 blunt-nosed minnows, 2 horned dace, 

 and 69 shiners, 18 more of the last coming from the Fox River water. 

 The seines gave us fifty-eight specimens of fifteen species; and 

 the dynamite explosions, sixty-seven specimens of six species. Only 

 two of the latter, the carp and the horned dace, were secured by 

 dynamite which did not also come out in the seines. The following 

 is the complete list. 



