Baker—The Fauna of The Lake Winnebago Region, 117 
Quantitative studies of the composition of the bottom fauna of 
the sea have been carried on for a number of years (see Petersen, 
1911, 1915, etc.) but similar studies on the biota of inland lakes 
are of comparatively recent date (Baker, 1916, 1918; Ekman, 1915; 
Muttkowski, 1918). Petersen (1911, p. 71) has said that we must 
know the main points concerning the productibility of a body of 
water before that body can be exploited for fishery purposes. This 
statement applies even more forcefully to the inland waters be¬ 
cause here the problems are in a measure simpler and fish culture 
is more easily controlled. Studies of this kind have been carried 
on by both counts of the number of animals found in a measured 
unit area and by weighing the dry animal matter of a unit area. 
Both methods are useful and should be used wherever practicable. 
In the Lake Winnebago work, which was conducted primarily to 
ascertain the number and kind of mollusks in Lake Winnebago and 
surrounding waters, only the counts of unit areas were made. 
Table 1 shows the numerical results for the Mollusca, together 
with the associated animals, in the different physiographic regions. 
The depth of the water is given in meters and the character of the 
bottom is indicated. The figures indicate the number of individ¬ 
uals per square meter of bottom. In the mollusks, the identifica¬ 
tion has been carried to all varieties; in the associated animals, only 
the larger groups are recorded. 
Lake Winnebago 
The Littoral Region, This is the most profoundly affected of 
any part of the lake area, including in its territory the shore with 
its breaker line where the physical forces are constantly at work. 
The littoral area may be divided into three quite characteristic 
subdivisions; 1, the general shore line; 2, the breaker line; and 
3, the plant areas. The first two divisions often overlap, and in 
the present paper will be considered under the several headings 
of boulders, sand, etc. The shore line is subject to great physio¬ 
graphic changes owing to the molar activity which causes the bot¬ 
tom to constantly shift more or less. Ecological conditions are 
here severe, the shifting bottom, the exposure to wide changes in 
temperature, and the pounding of the waves compelling the biota 
to make frequent readjustments to the environment. It is here 
that the greatest diversity of molluscan life occurs and the species 
