266 
stations included in this discussion number in all 648, distrib- 
uted as follows: Illinois River 235, Spoon River 36, Quiver 
Lake 115, Dogfish Lake 48, Flag Lake 44, Thompson’s Lake 99, 
and Phelps Lake 67. 
ILLINOIS RIVER CHANNEL, STATION E. 
(Table III.; Pl. L., V., VII.—XIII.) 
DESCRIPTION OF LOCALITY OF COLLECTION. 
The collections were made two and a quarter miles above 
the city of Havana, a short distance above the outlet of Quiver 
Lake (Pl. II.), at a point where the river was about 500 feet 
in width at low water and about 600 feet from crest to 
crest of the banks, which are here fringed by willows (Salix 
nigra and S. longifolia) on both sides. The eastern shore is a nar- 
row spit, 6 to 8 feet above low water, separating the river from 
Quiver Lake. The western bank is higher, 8 to 10 feet, and is 
covered by bottom-land forest. This is also a spit or “towhead” 
between the river and Seeb’s Lake. At low water (Pl. IV.) the 
eastern bank is exposed asa gentle declivity of 25 to 40 feet, 
while the western one is much wider—a belt, 50 to 75 feet in 
width, of soft black mud with gaping cracks (Pl. V.). A short 
distance from the low-water shore-line the bank shelves some- 
what abruptly to the bottom, which with the exception of a 
slight ridge near the center of the channel extends in an un- 
broken level from side to side of the stream. The depth at low 
water for a width of over 400 feet is 8 to 9 feet. To the north- 
ward the river deepens slightly, while towards the mouth 
of Spoon River it shoals to 6 feet, and below it to less 
than 5 feet. The banks are of black alluvium, hardened 
in the upper levels by exposure at low water, but al- 
ways soft and treacherous near the low-water line. The bot- 
tom in the channel is firm, being a compact bed'of heavy blu- 
ish mud mingled with sand and the shells of Unionide, which 
form in many places continuous beds of large area. 
A slight curve in the river above our plankton station shifts 
the current at that point towards the eastern shore, but at the 
