Abstract
Eight of the crinoids described by Rowley (1904) are redescribed and reclassified. This material is from northeastern and southeastern Missouri and was believed to include both Early Silurian and Middle Silurian material (Rowley, 1904). Reconsideration of this material changes considerably the interpretation of these fossils. All are assigned to a different genus with some assigned to a different order or subclass. Also, age assignments are clarified. Crinoids studied here that are considered to be probably Late Ordovician rather than Early Silurian are Calceocrinus alleni (previously Deltacrinus alleni), Ptychocrinus insperatus (previously Abludoglyptocrinus insperatus, Glyptocrinus insperatus, and G. insperatus var. carinatus of Rowley, 1904), Ptychocrinus pentagonus (previously Glyptocrinus insperatus var. pentagonus), Gnorimocrinus? problematicus (previously Gissocrinus? problematicus), and Glyptocrinidae genus unknown (previously Lampterocrinus? comptus). Two Middle Silurian (lower Ludlovian) crinoids that were described by Rowley are restudied, Thalamocrinus ovalis (previously Cyathocrinus? ovalis) and Clematocrinus dubius (previously Cordylocrinus? dubius).
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