418 
The Bottom Fauna of the Lakes and Ponds of the Illinois River 
Bottom-lands between Copperas Creek Dam and 
Lagrange, July—October, 1914—1915 
1. HyproGRaPpHY AND PHysIcaL FEATURES 
In the midsummer and autumn months of 1914 and 1915 a total 
of 266 bottom collections, principally with the mud-dipper, were made in 
the lakes and ponds and other backwaters in the river bottoms between 
the head of Clear Lake and the foot of Sangamon Bay, covering a river 
distance of 39 miles, and representing an ex-river acreage (about 16,000 
acres) at a gage of 8 feet, Havana, around one third of the total prevailing 
at the time between the Copperas Creek and Lagrange dams (about 52,000 
acres). : : 
The lakes and backwaters studied, separate naturally on a basis of 
physical and hydrographical features into five classes: 
I. The deeper lakes of the all-bottom-land type, with flat muddy 
banks on both sides, and with maximum depths at recent midsummer 
levels between 714 and 9 feet. The five lakes of this class examined— 
Clear—Mud, Liverpool, Thompson, Dogfish, and Sangamon Bay—have 
deep soft black mud bottom in the central deeper portions, and only 
rarely a little sand near shore. The vegetation, principally Potamogeton 
and Ceratophyllum, is confined to the rather wide shallow margins, the 
most of it well within the zone of 0—6 feet. These lakes ranged in size 
at the low water of 1901 (4.2 ft., Havana) from 275 to about 1,800 acres, 
and represented in all at that gage about 3,390 acres. At the average 
gage of July—October, 1910—1914 (approximately 8 ft., Havana), their 
acreage is somewhere near 214 times the 1901 figures, or over 8,000 
acres, which is close to one seventh of the total lake acreage between 
Copperas Creek dam and Lagrange, and more than the total river acreage 
at the same gage in the same distance (about 6,000 acres). 
II. The deeper, sand-beach type, bordering on one side against the 
sandy bluff, and with sandy shore on that side, but with flat muddy banks 
opposite. The two lakes of this type studied (Quiver and Matanzas) 
had a total acreage at the low water of 1901 of more than 600 acres), and 
maximum depths at recent midsummer levels of 8% to 12 feet. In 
Quiver Lake there is some sand and large quantities of old shells mixed 
with the mud in the deep “channel” which is kept open by the water from 
Quiver Creek during freshets. In Matanzas Lake the central open por- 
tion has all a soft black mud bottom. The vegetation in these two lakes 
is in its character and in its distribution not essentially different from 
that of the lakes of Class I, though it is inclined to be rather less dense 
on the average. These lakes receive a comparatively large amount of 
spring water from the sandy bluff on the east side, and their waters 
average somewhat clearer and (except at times of invasion by river 
water) poorer in plankton than the lakes of the all-bottom-land type. 
