396 
two stations in the shallower swifter section of 7.8 miles between the 
dam and Mile 129 (1 mile above Liverpool) ; and at two stations in the 
deeper more stagnant section of 9 miles between Mile 129 and Havana. 
Although the entire section of over 16 miles is on the average 
richer in small bottom animals than any other sections heretofore 
treated, biologically, as well as in its hydrographical characters, it is sep- 
arable into two well-distinguished portions, the half with the richer 
channel bottom fauna being the deeper muddier section below Mile 129 
and more immediately above the high Spoon-River bar. The average of 
the poundages per acre at the channel stations in the lower half of the sec- 
tion (5,156.0 lbs.) was in fact nearly six times the average valuation of 
channel above Mile 129 (878.3 Ibs. per acre), and almost fifteen times 
the average valuation at the channel stations between Chillicothe and 
the foot of Peoria Lake, Peoria Narrows excepted (345.1 Ibs.). 
Bottom Fauna, 1915, Copperas CrEEK Dam TO HAVANA 
POUNDS PER ACRE (AVERAGE TOTAL) 
Channel| 4—7-ft. zone 1—-ft. zone 
1. Copperas Creek dam to Mile 129 
(7.8 miles) No collections 
878.3 1,436.2 
2. Mile 129 to Havana (9 miles) | 5,180.8 2,122.0 | 919.7 
In the channel collections both above and below Liverpool the 
larger Viviparidae made up more than 99% of the weight of the average 
collection. The Sphaeriidae and the smaller Gastropoda amounted in 
weight to a mere trace in comparison; while the insects, worms, and 
small Crustacea accounted for less than half of one per cent. of the 
average poundages. 
Bortom Fauna, CHANNEL, Copperas CREEK DAM TO 1 MILE ABOVE 
LivEerRPoon, 1915 
Eee Small 
Viviparidae | Gastropoda | Insects, 
and and worms, Total 
Pleuroceridae | Sphaeriidae |Crustacea 
Number per sq. yard, 
Average 263.4 0.3 28.3 292.0 
8 coll.’s 
Pounds per acre, 
Average 874.2 0.1 4.0 878.3 
8 coll.’s 
Per cent. of total, | 
(By weight) 99.5% trace 0.4% 
