Baker—Molluscan Fauna of Tomahawk Lake, Wisconsin. 223 
MOLLUSC AN SUCCESSION. 
Tomahawk Lake presents a unique example of molluscan 
succession, a condition due to the raising of the water for storage 
purposes. So markedly has this change of level altered the 
shore in many places that a complete revolution has taken place 
in the biota. Originally, the lake was encircled by sandy shores 
with hut few swampy areas. The elevation of the lake level has 
changed this condition in many places, and at the present time 
swamps are abundant along the shore. All of the low flats have 
been submerged, the points extending under water for a con¬ 
siderable distance as sandy beaches and the low flats forming 
swamps or bays, the dead trees standing in three or four feet 
of water. 
Succession here has been in reverse order from that usually 
seen, i. e., the encroaching of one plant and animal society upon 
another, causing in the case of a pond, its gradual filling up and 
destruction. It has here been a change from dry land to 
swamps. However, it will be studied from the usual point and 
its artificial origin will be ignored in the present discussion. 
Stations V, XI and XIV, are the best examples of succession. 
Primal Condition, the Open Lake Shore. 
(Figures 4, 5.) 
In this primal stage, the shore is bordered by a shelving, shal¬ 
low, sandy beach, which is subject to wave action to. a greater 
or less degree. Such mollusks as the following occupy this hab¬ 
itat: 
Lampsilis luteola. 
Anodonta marginaia. 
Anodonia grandis footiema. 
Sphcerium simile. 
Compeloma decisum,■. 
Physa ancillaria warreniana. 
