374 
Speaking generally, the richest sections of the river floor are those 
with the least average slope and the slowest current, and therefore with 
the most abundant sediments. The quantity of the bottom fauna dimin- 
ishes rapidly down-stream from Chillicothe, averaging 555 pounds to the 
acre for the upper sixty miles (the weight of the shells of the mollusks 
being in all cases deducted), 88 pounds for the forty-two and a half 
miles next following, and 10.4 pounds for the lower seventy-seven miles. 
The general average for the river channel from Chillicothe to the mouth | 
was 261 pounds per acre. That for Copperas Creek to Lagrange, within 
which section lay the twelve principal lakes studied, was 705 pounds per 
acre, and the highest sectional yield was 2,693 pounds per acre between 
Copperas Creek and Havana. The highest local yield was found in the 
lower half of this Copperas Creek-Havana section, whose channel prod- 
uct rose to 5,196 pounds per acre. These enormous yields in the 
stretch above Havana were evidently due, at least in great measure, to 
the sluggish current and consequent heavy sedimentation and to the 
great predominance (99 per cent.) of relatively large, thick-shelled snails, 
edible only by the larger fishes, armed with a powerful crushing apparatus 
in jaws and throat. 
In the muddy section of river above Havana the channel yields ap- 
proximated or even surpassed those of the shallow waters along shore; 
but below Havana, where mud is largely replaced by sand, clay, or shells, 
the channel yields were only 5 to 10 per cent. those of the longshore 
zone. 
Comparing river and lakes between Copperas Creek and Lagrange 
(59.3 miles) we find that the average bottom yield per acre of twelve 
lakes examined was about one third that of the river opposite them, 
but that it was practically the same as the average for the entire river 
from Chillicothe to the mouth. The deeper lakes with sandy beaches at 
one side yielded about twice as much per acre as the shallower lakes with 
mud banks all around. 
In the deeper bottom-land lakes surrounded by mud banks, the shore 
belt, to a depth not exceeding six feet, yielded about three times as much 
bottom fauna per acre as the deeper open water of these lakes; but-in 
the sand-beach lakes this relation was reversed, the deeper bottom yield- 
ing five or six times as much as that within the 6-foot line. 
The foregoing statements all apply to the animals living in or on 
the bottom muds; but in the shallow, weedy areas of lakes and back- 
waters the small invertebrate animals living on and among the weeds 
greatly exceed both in number and in weight per acre the fauna of the 
bottom itself, aggregating in many collections made near Havana in 1914, 
from 1,100, to nearly. 2,600 pounds per acre, with an average of 2,118 
pounds—quantities to be compared with an average of 255 pounds of 
bottom fauna per acre from the lakes of the same district. 
Combining weed and bottom faunas of our collections and las 
their joint averages to the entire area of lake and backwater between 
