190 THE AMERICAN MIDLAND NATURALIST. 
For assistance in checking reports and records, and in 
editing of the manuscript, I am indebted to Mr. Ira N. Gabriel- 
son, Dr. Lynds Jones, and Miss Althea M. Sherman. The late 
Dr. B. H. Bailey, of Coe College, Cedar Rapids, examined 
manuscript and specimens, checking virtually all the material 
in hand in 1916. Finally, the entire manuscript, in virtually 
its present form, has been read by Dr. T. C. Stephens, of 
Morningside College, who has made copious notes and valued 
suggestions. 
II]. —GEOGRAPHY OF FLOYD COUNTY. 
A.—TOPOGRAPHY. 
Floyd County lies within the area covered by the Iowan drift 
sheet. In general its surface is gently rolling, with no very 
deep valleys or bold hills, and few to many undrained de- 
pressions, depending upon the exact spot under considera- 
tion. On the whole it may be considered as typical of what 
McGee has styled the “rolling Iowan” prairies. 
The largest stream in the country is the Cedar (more 
properly, Red Cedar) River, which flows southeastward 
through the county. It is a broad, rather sluggish stream 
stopped by a large dam at Charles City, and a small, dilapi- 
dated one at Floyd. The Charles City dam causes a con- 
siderable widening of the stream, and assists somewhat in 
the formation of marshy “bayous” northwest of the town. 
North of Floyd the river banks are high, and in some places 
steep, with prominent limestone faces, but near and south 
of Charles City the banks are low and gently sloping. 
Flood Creek, a small stream, flows roughly parallel with 
the Cedar River, but several miles west of it. Its banks are 
low, and very largely of drift. 
The Shell Rock River parallels Flood Creek in the western 
part of the county. It is similar to, but considerably smaller 
than the Cedar River, and its.banks are somewhat steeper. 
Its tributary, Lime Creek, flows through Cerro Gordo county, 
entering Floyd northwest of Rockford. For a considerable 
distance it flows through a broad, flat valley at the base of 
clay hills sixty to eighty feet in height. The most abrupt 
