130 Wisconsin Academy of Sciences, Arts, and Letters, 
and bordered by marsh vegetation. Aquatic plants grow in the 
shallower parts of the river. Mollusks were most numerous near 
the shore on a sand or mud bottom in water 0.5 to 1 meter in depth. 
The Naiades are mostly different from the lake species as noted 
under Lake Winnebago species. The gastropods are mostly of 
species living in quiet habitats and there is not the variety found 
in the lakes, the latter being 50 per cent richer in species. Of the 
population of the river habitats Sphaerium striatinum makes up 
67 per cent, forming great beds bordering the shore in many places. 
Quantitative Analyses of the Fauna 
On rocky shores, a number of boulders were measured, the total 
animal life removed, and the area computed to the square meter 
unit. In the vegetation stations the total area covered by the plants 
was computed to the same unit. In several cases, as in Scirpus 
habitats, the unit included a column from surface to bottom. 
The population of Lake Winnebago compares favorably with 
that of any lake studied, being exceeded only by Oneida Lake 
among American inland lakes. The average number of animals 
per unit area on the different kinds of bottom in the two lakes 
mentioned is shown in table 2. 
It will be seen that among the Mollusca, Oneida Lake is 59 per 
cent richer, while among associated animals. Lake Winnebago is 
9 per cent richer in individual population. The small population 
of the vegetation habitats in Oneida Lake is due to the fact that 
much of the population is included in the bottom areas which had 
an algal covering. 
Table 3 shows that Oneida Lake has a greater population per 
unit of area in the shallower water, but that Lake Winnebago has 
a greater population in the deeper water. Lake Mendota has a very 
small population in the shallow water as compared with the other 
lakes. Lake Butte des Morts has the largest population in the 
deeper water as well as the largest total population per unit area. 
The molluscan fauna of the Winnebago region is one of the 
most extensive and varied of any similar area yet studied. A total 
of 114 species and varieties of fluviatile and lacustrine forms were 
found, including three forms believed to be new to science. Table 
4 shows the relative abundance of the molluscan fauna in the dif¬ 
ferent parts of this region. 
