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STATION IX. 
A small pool to the southeast of Station VII, and connected with 
that habitat by an area of low swampy ground, forming a depression 
in the high ground surrounding Station VII. Area about fifteen 
by twenty-five feet. The vegetation is the same as that of Station 
Vil. 
This station is carpeted with 
Ranunculus multifidus. Yellow Water-Crowfoot. 
Proserpinaca palustris. Mermaid-weed. 
The following mollusks were observed, Physa gyrina being the 
predominating species. 
FLUVIATILE SPECIES. 
Spherium occidentale. Rare. 
Musculium partumeium. Common. 
Physa gyrina. Abundant. 
Planorbts trivoluis. Common. 
Segmentina armigera. Common. 
Lymnea reflexa. Rare. 
LAND SPECIES. 
Succinea retusa. Common. 
Agriolimax campestris. Common. 
Lymnea reflexa is a migrant from Station VII. 
STATION: .X. 
A small pond about thirty feet in diameter, almost circular in 
outline, two hundred or more feet from the larger pond (Station 
VII), and connected with that station by a narrow stream of water. 
The pond hole is from six inches to two feet indepth, and the bottom 
is composed of soft, tenacious, clayey mud. In the spring the hole 
is filled with water, but during the summer and fall the water 
evaporates, leaving the mud in hard, irregular cakes, the cracks 
between being filled with vegetation. The mollusks find a retreat in 
these cracks, into which they crawl and estivate. An epiphragm 
is formed, as in the helices, and many individuals are thus enabled 
to survive the dry summer, to be revived in the late fall when the 
rains begin, thus providing for the perpetuation of the species. 
Physa gyrina is the most abundant species in this station, the dead 
