Freshwater Mussels Devt 
This is also observable at one point on the east shore—the north side of 
Boys’ City Bay—(Map, D) and at one point on the north shore, (Map, 
U) which lie somewhat parallel to the prevailing winds. 
TABLE I. 
Correspondence of Species to Type of Bottom. 
Section Anodonta grandis Lampsilis luteolus Bottom character Remarks 
present present 
D 18 23 Marly: samidie omo! ay Aes Wyse as eto ee 
Marly mud 
O 31 2 Meryasobtrapet cot r mil, eas. 5 ykn eae 
I—K 14 39 Band yerty ls + Aiea ois |/k ee rae a one ale 
E 10 6 Soft marl All small 
Ki a 9 12 Marly sand 
b 31 16 Marly mud See Figure 1 
L 42 52 Marl’ midlets Way kaye eae he seam 
Z 3 33 Firm, marly sand “Sunken Island” 
Section K, will illustrate very well how the gradation in bottom is 
followed in the distribution of the two species. (Table I and Fig. 1.) 
The sandy portion has fewer Anodonta than Lampsilis, while the adja- 
cent muddier part has twice as many Anodonta as Lampsilis. Section L 
is subject to similar comparison. Such comparisons can be made between 
areas in the above table, except Section E. 
Headlee and Simonton relate that mussel beds at Stations E to I 
were covered twenty years ago with mud from dredging operations. To 
this day many dead shells are found in those areas, and few living 
mussels. I was long at a loss to explain the occurrence of so many dead 
shells where there were almost no live ones. Even today they have 
secured a new foothold only in the more or less exposed places (e.g. 
Section G.) 
The extremely soft bottoms of the canals and Section N of the lake 
are inhabited by Sphaeriids, but not by Unionids. In the latter some 
dead shells are found. ' 
Evermann and Clark’s observations of the distribution in Lake 
Maxinkuckee (’17) show that there the greater part of the bivalve 
population lies within the shoreward contours, and that deeper dredg- 
ings bring up more Anodonta than Lampsilis. Baker (718) finds by far 
the greater part of the invertebrate life of Oneida Lake within the six 
foot contour, the bivalves lying more deeply than the other invertebrates. 
My collecting in Winona Lake shows that the mussel zone of Winona 
Lake is in somewhat shallower water. We might expect this in a small 
kettle hole lake, whose littoral is chiefly a wave cut terrace, going off 
sharply into deeper water at its outer margin, and itself averaging 
less in depth than in such a lake as Oneida. Being formed by waves 
and currents, it tends to be shallower and narrower in lakes too small 
for large waves. Headlee and Simonton’s map indicates that the mussel 
life belongs predominantly within the ten-foot contour. While they 
found live mussels out to a depth of twenty-two feet, the deeper ones 
were all narrowly limited to exposed points, which the undertow keeps 
swept clean, and on the lee shore, where the thermocline may sometimes 
be depressed. Aeration and food must be better at such points than at 
others of equal depth. 
