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Mollusks of the following species were secured, all fluviatile: 
Spherium occidentale. Rare. 
Musculium partumeium. Common. 
Segmentina armigera. Common. 
Aplexa hypnorum. Very common. 
Physa gyrina. Common. 
Lymnea caperata. Common. 
Lymnea reflexa. Rare. 
Lymnea reflexa is undoubtedly a migrant from Station VII, prob- 
ably floated down during high water. But two specimens were 
found after a careful search. 
STATION XII. 
Woods bordering Station XI. The ground is low and conse- 
quently wet in spring. Succinea ovalts was observed on leaves of 
various plants, four to five feet from the ground. It was also found 
under dead leaves. In summer this area is dry and the ground is 
quite hard. 
The following land mollusks were secured : 
Succinea avara. Rare. 
Succinea retusa. Rare. 
Succinea ovalis. Common. 
Polygyra thyroides. Uncommon. 
Polygyra fraterna. Common. 
STATION XIII. 
Wet portions of woods connecting stations XII and XIV, evi- 
dently fed by overflow from Station XIV. 
Vegetation the same as that of Station XI. 
The following species of mollusks, all fluviatile, were secured. 
OF the first three species, the Lymnea was the least abundant and 
the Aplexa the most abundant. 
Spherium occidentale. Common. 
A plexa hypnorum. Very common. 
Lymnea caperata. Uncommon. 
Planorbis exacuous. Rare. 
STATION XIV. 
(Plates XII.,2, and XIII.) 
A small pond about thirty feet in diameter, rather pyriform in 
shape. The water is knee to waist deep in the spring, but in the 
