• Outcrop of the St. Peter Sandstone in St. Paul, Minnesota. The St. Peter is
• the basal formation of the Middle Ordovician Tippecanoe Sequence.

• The Middle Ordovician Galena Group limestones at
• the Rifle Hill Quarry, near Greenleafton, Minnesota

 

• A typical Middle Ordovician brachiopod - bryozoan slab from the
• Decorah Shale, Spring Grove Quarries, Minnesota

Isotelus - a characteristic trilobite from theOrdovician formations of Minnesota

Part of a large orthoconic nautiloid from the Platteville
Formation, Middle Ordovician, Spring Grove, Minnesota