226 Wisconsin Academy of Sciences, Arts, and Letters . 
would contain (as several stations in tins area have been found 
to). 
Musculium rosaceum. 
Pisidium roperi. 
Ancylus parallelus. 
Planorbis parvus . 
The fresh-water species have here been reduced to five species. 
Land Shell Succession. 
Figure 13. 
Should this area become dry it would soon be covered with 
such trees as birch, white spruce, tamarack, etc., and the follow¬ 
ing land mollusks would completely replace the fresh-water pul- 
monates. 
Helicodiscus parallelus. 
Pyramidula cronkhitei catskillensis. 
Zonitoides arboreus. 
Vitrea hammonis. 
Strobilops virgo. 
Though not observed continuously in one place, the above five 
successions have been seen within a radius of one mile; the first 
three, however, have occurred in one small area, during the few 
years which have passed since the water was raised. 
