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. 



