86 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[184 



putrescent matter is not quite as abundant as higher up in the canal 

 and the odor is not as bad. 



Samples were collected from a point about a mile above the junction 

 of Salt Fork with the Spoon River. Organisms were fewer in both species 

 and individuals. 



Blue-green algae 



Phormidium inundatum, common. 



Diatoms 

 Synedea pulchella, abundant. 

 Fragilaria capucina, abundant. 



Animals 



CUiata, abundant. 

 Euglena geniculata. 

 Limnodrilus, a few individuals. 



Below the mouth of Spoon River conditions are also bad. Where the 

 current is strong, sand bars have been formed which cover the black mud 

 beneath. Everywhere, except in the channel where it is sandy, the bottom 

 is of soft mud, eight to fifteen inches deep, filled with ill-smelling gasses. 

 Sewage conditions here are bad, the water having a foul smell. When 

 wading in the water, the disturbed mud, which is black and oozy, con- 

 stantly gives off bubbles of gasses that rise to the surface and break. This 

 condition is uniform for the entire stretch of stream bed examined, about 

 a third of a mile, from near the mouth of Spoon River to the middle of the 

 big bend above St. Joseph. The surface of the water is usually covered 

 with a film of oil resembling petroleum. 



No living mussels could be found in this area. A single valve of Am- 

 blema undulata was seen near the mouth of Spoon River which was prob- 

 ably brought to its resting place from Spoon River during a period of 

 flood. It is noteworthy that while no mussels or gill-bearing snails were 

 observed in this part of Salt Fork, several species of fresh water pul- 

 monates were seen in considerable numbers, indicating that here, as 

 elsewhere, the pulmonates are able to live in water which is totally 

 unfit for mussels and gill-bearing moUusks. 



Examples of the bottom sediments and green masses floating in the 

 water were taken from the stream about a hundred feet below the mouth 

 of Spoon River. Algae was plentiful and included Phormidium inundatum, 

 a blue-green species, in abundance. Tv/o species of diatoms, Navicula 

 salinarum and Fragilaria capucina, were also present. Of animals, Limno- 

 drilus was well represented, but Euglena geniculata was not common, and 

 ciliate Protozoa were much less numerous than in samples taken from 

 stations higher up in the stream. Salt Fork here shows the influence of 

 the added cleaner water from Spoon River. 



At the mouth of Spoon River a bar has been formed, by natural or 

 artificial agencies, which, except for a space about four feet wide, holds 

 back the waters of that stream (Fig. 16). An examination was made 

 of Spoon River about 400 feet above this bar. Here five species of mussels 



