FORMATIONS IN SOUTHEASTERN IOWA. 299 
CHARACTERISTICS OF THE FORMATIONS. 
The Warsaw shales and limestones.—A consideration of the 
given sections will show that, at the original locality, the War- 
Saw group consisted of three members, viz., a bed of magnesian 
limestone at the base, arenaceous limestone or calcareous sand- 
stone at the top with argillaceous shales, including thin and 
variable beds of limestone between. Of these the last is the most 
persistent. The basal division which is twelve feet thick at War- 
saw diminishes to three or four feet at Keokuk and is not recog- 
nized north of that place. The middle division, however, 
unchanged in character but greatly diminished in thickness, is 
recognized at Farmington, Rock Creek and doubtfully at several 
other localities. The shales and lmestones evidently thin out 
entirely near the north line of Lee county. The formation is 
prominently characterized by Bryozoa, among which species of 
Archimedes, Fenestella and other reticulated forms are conspicu- 
ous. With these are associated other forms constituting a some- 
what peculiar assemblage of fossils, though on the whole allied 
to those of the Keokuk group. In the Illinois reports, the 
peculiarity of the fauna is admitted but is considered of some- 
what local development, and is attributed to local conditions of 
sedimentation rather than to any specific change in the character 
of the fauna. A somewhat similar assemblage of fossils at 
Bloomington and Spergen Hill, Indiana, was referred to by Hall 
as proving the existence of these beds in that state. As later 
collectors have referred the fossils obtained from these beds to 
the horizon of the Saint Louis limestone without specific designa- 
tion of the beds from which they were obtained, new collections 
must be made before the exact relations of these deposits can be 
considered established. 
Evidently, however, the formation is not of wide extent and 
probably represents only a comparatively local development of 
the geode shales into which they grade below. It is suggestive 
in this connection that the geode shales have their most charac- 
teristic development coincident with that of the Warsaw shales 
and limestones, and both soon lose their distinctive characters 
