The Chesterian Series, the uppermost series of the Mississippian System, is named for Chester, Randolph County, where it is well exposed in the bluffs of the Mississippi River. The Chesterian Series consists of limestone-shale formations alternating with sandstone-shale formations. It extends from the major unconformity at the base of the Pennsylvanian System (sub-Absaroka unconformity) down to the base of the Shetlerville Member of the Renault Formation, which is the top of the Valmeyeran Series. Many of the Chesterian limestones and shales are abundantly fossiliferous. The sandstones are much less fossiliferous, but can contain some plant fossils. Coals, a few inches thick at most, occur in some of the Chesterian sandstones. Many of the limestones contain abundant crinoidal fragments, and the series is characterized by the presence of Talarocrinus which distinguishes it from the underlying Valmeyeran containing Platycrinites penicillus. Blastoids and the corkscrew bryozoan, Archimedes, are common and characteristic.