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INTRODUCTION 
This paper has assumed its present title and form from the 
necessity of conforming to the first needs of investigation con- 
cerning the ecological relations of the animals in the region with 
which it deals. The original intention of the writer was to 
analyze briefly the chief animal habitats afforded by Johnson 
County and to carry on a series of intensive studies of the animals 
forming the various associations in these respective habitats with 
the hopes of drawing some large conclusions as to the reactions 
and interrelations of such groups of animals. This plan was 
discontinued in favor of the one upon which this paper is now 
based for the following reasons: (1) the lack of definite infor- 
mation as to the location of particular habitats, their extent, 
accessibility, ete., from which to carry on such investigation ; 
(2) the immediate necessity of compiling and placing on record 
available information in accessible form as a nucleus for future 
intensive studies; (3) the urgent desirability of having a de- 
scriptive atlas bearing this information of the country immedi- 
ately surrounding the University of Iowa for the use of workers 
in this institution; and (4) the wish to make a typical survey 
and atlas of one county of the state as a precedent for work in 
other localities. _ 
This paper is further intended to bring together all of the data 
pertaining to this region, such as topography and climate, that 
shall be pertinent to any interpretative studies of the animal 
life. Emphasis, therefore, is laid upon the habitat rather than 
upon the fauna, and all attempts at detailed discussion of the 
various animal associations have been omitted. Numerous refer- 
ences are made to the animal life throughout the text, but care 
has been taken to keep these in the form of general statements, 
in order to prevent diversion of the emphasis of the treatise. 
For this same reason the scientific names of species have not 
been given. 
