30 ILLINOIS BIOLOGICAL MONOGRAPHS [128 
It is noteworthy that with a length of 300 miles and with two tributa- 
ries of large size (Iroquois River, 100 miles in length, Yellow River, 65 miles 
long) the Kankakee River has a mussel fauna only 21 per cent greater than 
the Big Vermilion River with a length of 90 miles and no very long tribu- 
taries. Other species will proably be found in the Big Vermilion below 
Danville, which was not examined during this survey, and these may 
bring the total nearer to that of the Kankakee River. The Sangamon 
River undoubtedly contains many more species than listed in the table, 
and these will be found when additional collecting is carried on. The table 
shows that the mussel fauna of the Big Vermilion River is of large size as 
compared with other streams of similar character. 
