ArTICLE IV.—The Ecology of the Skokie Marsh Area, with 
Special Reference to the Mollusca. By FRANK CoLLIns BAKER. 
INTRODUCTION. 
The present paper is an attempt to place on record a minute 
study of a small area with special reference to its molluscan inhabit- 
ants. It is believed that this is one of the first attempts to apply 
the ecological method, so notably used by the botanists (Cowles, 
1901; Jennings, 1909, etc.), to the study of the Mollusca, although 
Adams (1906) and Ruthven (1904) have included this class of ani- 
mals in their report of the Ecological Survey of Michigan, and 
Pilsbry (1905), Elrod (1901-03) and Adams (1900) have made valu- 
able contributions to molluscan ecology. Attempts to study the 
mollusks of a restricted region from an ecological standpoint are, 
however, rare, the writer having been unable to find any papers in 
which these animals were studied purely from this standpoint. 
It was thought that an exhaustive study of the habitat relations 
of all the mollusks of a given area might throw some light on their 
specific distinctions (especially those of the fresh-water pulmonates), 
and the studies herein detailed seem to warrant the belief that some 
good results along this line have been accomplished. These are 
referred to under the head of taxonomy (page 489). 
METHOD OF STUDY. 
The area in question was visited once or twice a week from May 
18 to September 5, 1908; some additional work was also done in 
1909. Many of the stations were visited several times, and nearly 
all were examined twice or more. Specimens were collected from 
the edges of the pools and ponds as well as from the deeper parts. 
In the woods almost every old log and piece of rotting wood was 
examined, and in the dry ponds the ground was dug up in many 
places in search of any burrowing mollusk. All material has been 
carefully preserved with exact data, and now forms a part of the 
ecological collection of the Chicago Academy of Sciences. 
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