428 
ILLINOIS VALLEY LAKEs, 1914—1915, Borrom Fauna 
POUNDS PER ACRE 
I. Deep Bottom-land Type. (Zone over 6 feet) 
Large 
No. col- Bae 3 Sphaeriidae | Insects Per cent. 
Lake lections Mafra: etc. etc. Total Mollusca 
Clear—Mud, 1915 8 17.1 186.8 11.7 215.6 | 94 
Liverpool, 1915 6 24.3 96.7 | 21.2 142.2 | 85 » 
Thompson, 1914 8 76.5 140.0 94.2 310.7 | 69 
Thompson, 1915 8 413.9 64.6 18.1 496.6 96 + 
Dogfish, 1914 3 8.0 3.1 12.3 23.4 47 
Dogfish, 1915 12 67.1 18.5 66.4 152.0 56 
Sangamon, 1915 10 51.2 41.4 14.0 106.6 86 
Average 53 104.6 82.2 35.2 222 84.1% 
ILLINOIS VALLEY Lakes, 1914—1915, Botrom Fauna _ 
POUNDS PER ACRE 
1. Deep Bottom-land Type. (1—6-ft. Zone. No Vegetation) 
No. col- Large : 
Lake ‘easton Viviparidae| Sphaeriidae |Insects| Total | Per cent. 
: - ete. ete. etc. Mollusca 
Thompson, 1914 10 687.1 80.3 135.8 903.2 85 
Thompson, 1915 7 610.5 24.9 12.2 647.6 98 
Sangamon, 1915 4 145.3 109.5 10.2 265.0 96 
Average 21 558.3 67.3 70.6 696 89.8%, 
