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 Animals 
Phormidium inundalum, common. Ciliata, abundant. 
Diatoms Euglena geniculata. 
Synedea pulchella, abundant. Limnodrilus, a few individuals. 
Fragilaria capucina, abundant. 
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 mollusks. 
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. ‘Two 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 
