14 ILLINOIS BIOLOGICAL MONOGRAPHS [112 
at this place would be quite normal for the life of mussels and other bottom 
animals. (See the chapter on sewage pollution.) 
Several other river systems have their beginning near Urbana and 
Champaign, on the southwest side of the Champaign moraine. These are 
the Embarras, which has tributaries rising south of Urbana; the Kaskaskia, 
which has its inception northwest of Champaign near the village of Rising; 
the Little Vermilion, which rises in the southeastern part of Champaign 
County; and the Sangamon, which rises in the extreme northwestern part 
of Champaign County not far from Gibson. Only the last stream has been 
examined for its mussel] fauna for the purpose of making comparisons with 
the fauna of the Big Vermilion River. 
The Sangamon River has a length of about 180 miles and a drainage 
basin of some 5670 square miles. It rises on the south side of the Blooming- 
ton moraine in McLean County,“at an elevation of 850 feet above sea 
level, and cuts through two moraines in its course, the Champaign and the 
Shelbyville. The river channel is tortuous and meandering and the flood 
plain in many places very wide. The banks of the stream are low for the 
most part and wooded in spots. The stream has been examined carefully 
at only two points, Mahomet and west of White Heath, the first locality 
receiving the most attention. Near Mahomet the river is notably mean- 
dering, the banks are high, the Champaign moraine rising 90 feet above 
the water level near the village. The river bank is usually five or six feet 
above the stream, which has cut vertical cliff-like banks in many places. 
Below Mahomet the woodlands are abundant, extending well back from 
the river in some places. The river varies in width from 40 to SO feet. 
The bottom alternates between riffles with sand and gravel bottom and 
deeper back water stretches with mud bottom. The former habitats are 
a foot or so in depth and the latter habitats two to four feet in depth in the 
summer. In the spring the river is ten to twelve feet deep and very swift, 
at times becoming torrential. The average fall of the stream is 2.3 feet 
per mile. Many logs and other débris thrown up on the flood plains attest 
the power of the river during spring floods. 
West of White Heath, for a mile above the I. C. railroad bridge to 
two miles below, the river has been examined, though no systematic 
collecting comparable to that carried on at Mahomet has been done. The 
stream in the portion of the river valley examined is similar to that near 
Mahomet in its general physiographic features. The banks of the stream 
are on the whole lower than farther up the river near Mahomet. Studies 
of this stream similar to those carried on in the Big Vermilion and its 
tributaries would doubtless yield interesting and valuable results. The 
Sangamon is a characteristic mussel stream and should contain a much 
larger mussel fauna than at present known and listed. 
