407 
Bottom Fauna—In August, 1915, a total of 75 collections of the 
bottom animals were made in cross-section at 15 stations between La- 
grange dam and the mouth of the river, as shown in the preceding table. 
The bottom-fauna valuations indicated between Lagrange and Graf- 
ton by our collections of August, 1915, were almost uniformly poor both 
in the shore zones and in the channel—the average of the sixteen channel 
collections being only 6.7 Ibs. per acre; that of 31 collections between 
4-7-feet, 16.7 lbs.; and that of 28 collections within the 4-foot line, 16.9 
Ibs. The best local figures for the shore were obtained in the 4—7-foot zone 
opposite Meredosia, where two hauls averaged 57.5 lbs. per acre; and 
in the 1-3-foot zone below Kampsville dam, where twelve collections 
averaged 27.9 Ibs. Both in the channel and in the shore zones, if we 
except the 4—7-foot zone collections opposite Meredosia, Mollusca con- 
tributed less or very little more to the average weight of collections than 
did insects, worms, and small Crustacea, which together made up 63 to 
65% of the average weight of collections in those depths zones, with 
the noted exception. Of the latter group (non-Mollusca) the most im- 
portant in weight were the larvae of caddis-flies in the channel, and the 
immature stages of Ephemeridae (willdw-flies) in the shore zones. As 
these were principally of the new broods hatched from eggs deposited 
by the adults which emerged only a month to six weeks earlier, they 
contributed less to the weight of collections than they would have done 
in the same numbers earlier in the summer or later in the fall. The 
larger snails (Viviparidae and Pleuroceridae) amounted nowhere be- 
low Lagrange to more than 5 or 10% of the weight of collections. 
Borrom Fauna, 1915, LAGRANGE TO GRAFTON 
POUNDS PER ACRE (AVERAGE TOTAL) 
Att) 18 tt. 
Reach Channel aan care 
1. Lagrange dam to Florence (21.9 miles) Bie) 10.1 
4* 2 8 
2. Florence to Kampsville, above dam (24.2 miles) 12.4 16.6 105) 
5 Ty. 8 
3. Kampsville above dam to Grafton (31.4 miles) 6.5 10.3 27.9 
A 2 12 
Lagrange to Grafton (77.5 miles) 6.7 16.7 16.9 
: 16 21 28 
*The Italic figures give the number of collections. 
