Baker-—Molluscan Fauna of Tomahawk Lake, Wisconsin. 225 
Swamp Succession. (Figure 3). 
The water rises still higher and overflows meadow-like areas 
producing large open swamps (as at station XIII) or, small- 
ponded areas. The water is shallow, the bottom is usually 
muddy or boggy and the vegetation consists chiefly of Typha 
latifolia and several species of sedge. A considerable change is 
noted in the character of the mollusks. 
Musculium securis. 
Pisidium abditum. 
Pisidium subrotundum. 
Ancylus parallelus. 
Segmentina armigera. 
Planorbis hirsutus. 
Planorbis bicarinatus unicarinatus. 
Pla/norbis trivolvis. 
Planorbis binneyi. 
Lymncea stagnalis appressa. 
Lymncea megasoma. 
Lymncea lanceata. 
Succinea retusa. 
It will be noted that the Pelecypods are represented only by 
the small Musculium and Pisidium and the Gastropods all be¬ 
long to the fresh-water Pulmonates (excepting Succinea.) 
Only four species are the same as those in the previous succes¬ 
sion ( Ancylus, Planorbis hirsutus, Planorbis binneyi, Lym¬ 
ncea lanceata), nine species or about 66 per cent, being new to 
the environment. Only one species, Planorbis binneyi, persists 
throughout the last three successions. 
Swale Succession. 
Should the level of the water fall a foot or more, a fourth 
succession would develop in certain places, in which small 
swampy pools or swales would be developed. Such a habitat 
