Fenestella sp.
bryozoan

Mississippian
Meramecian Series
Warsaw Formation
St. Louis County, Missouri

 
Fenestella sp.

Order Fenestrata
Ordovician - Permian

Archimedes lived in the fenestrate fans
that spiraled out from the screw-like axis.
Alan Goldstein

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Warsaw Formation

Mississippian Fossils of Missouri