183] FAUNA OF BIG VERMILION RIVER— BAKER 85 



It seems evident that this portion of the old stream forms a reservoir 

 from which certain species of mollusks, as well as fish, are carried, or volun- 

 tarily migrate, through the outlet into Salt Fork. By this means only 

 can the presence of these animals in the polluted water be accounted for, 

 because none have been seen either above or far below the drain from the 

 old stream channel. The specimens of Planorhis trivolvis, that have been 

 observed in the Salt Fork canal below the east and west road bridge, were 

 probably derived from this source. 



Specimens of Planorbis trivolvis have been observed in the Salt Fork 

 canal which probably came from this source. Near this locality a school 

 of about fifty fingerling bullheads was observed on May 29, in a small 

 part of the stream where a rather deep pool had developed. They were 

 making frantic efforts to get out of the pool but the surrounding water 

 ^as too shallow. The low water and general polluted condition of the 

 stream evidently provided a very unfavorable environment. The source 

 from which these fish came was quite likely the old cut off portion of the 

 original Salt Fork from which place they had been carried or had volun- 

 tarily migrated, when the water was higher from the April rains. 



From the east and west road bridge (Fig. 45) to the first farmer's bridge, 

 a distance of about three-quarters of a mile, the conditions are the same 

 as in the preceding portion of the canal. The water is clear but no living 

 mollusks or other animals could be found. A half valve of Anodonta 

 grandis, badly weathered, and a few bleached valves of Sphaerium solidu- 

 lum, were the only evidences of molluscan life. These had evidently been 

 washed from the old stream bed at some point where it was exposed by 

 erosion in the canal walls. The same algae as previously observed was 

 floating down the stream in large green patches. Samples of these green 

 particles were examined by Professor Smith and found to contain such 

 animials as Euglena geniculata, Paramoecium, and numerous ciliate Pro- 

 tozoa, mostly inhabitants of polluted water. 



From the next farmer's bridge to the eastward turn of the stream the 

 bottom conditions were also similar, except that the surface of the water 

 was covered with an oily scum. Groups of greater or less size of gyrinid 

 beetles {Dineutes assimilis) were seen at different places down stream for 

 a mile or more. A single empty shell of Planorbis trivolvis was observed 

 on the shore of the west bank below this bridge. No living clams were 

 seen, nor any mutilated valves. 



From the eastward turn of the stream to the mouth of Spoon River, 

 the canal is in bad condition, the water being dirty and oily, with numer- 

 ous bubbles of gas rising constantly from the bottom, which also gave off 

 quantities of oily scum when disturbed (Fig. 44). The water is shallow 

 and conditions as already described for the stream higher up. Green 



