Species of the late Osagean and early Meramecian advanced cladid crinoid genera (suborder Poteriocrinina) Armenocrinus, Bollandocrinus, Corythocrinus, Cosmetocrinus, Culmicrinus, Cydrocrinus, Histocrinus, Hypselocrinus, Lebetocrinus, Ophiurocrinus, Poteriocrinites, Scytalocrinus, Springericrinus, and Ulrichicrinus from Illinois, Indiana, Iowa, and Missouri are redescribed and redefined from study of type material. Nomenclatural and systematic acts include the following: 1) Poteriocrinus tenuidactylus Worthen, 1882, is a senior synonym of Scaphiocrinus obscurus Wachsmuth and Springer, 1886, and is assigned to Armenocrinus; 2) P. verus Miller and Gurley, 1890, is assigned to Culmicrinus; 3) P. mammaeformis Worthen in Miller, 1889, is questionably assigned to Culmicrinus; 4) Cydrocrinus coxanus (Worthen, 1882) is a junior synonym of C. concinnus (Meek and Worthen, 1870); 5) Decadocrinus stellatus Lane and Howell, 1986, is questionably assigned to Histocrinus; 6) P. crawfordsvillensis Miller and Gurley, 1890, is a junior synonym of Hypselocrinus hoveyi (Worthen in Worthen and Meek, 1875); 7) Hypselocrinus boonvillensis (Miller, 1891) and H. neglectus (Miller and Gurley, 1896) are junior synonyms of H. arcanus (Miller and Gurley, 1890); 8) Hypselocrinus vansanti n. sp. is described; 9) Hypselocrinus indianensis (Meek and Worthen, 1865) is a nomem dubium; 10) Poteriocrinus arachnaeformis Worthen, 1882, is a valid species of Poteriocrinites; 11) P. cantonensis Miller and Gurley, 1890, is assigned to Scytalocrinus; 12) Ulrichicrinus coryphaeus (Miller, 1891), P. amoenus Miller, 1891, and P. brittsi Miller, 1891, are junior synonyms of U. agnatus (Miller, 1891); and 13) P. illinoisensis Worthen, 1882, is questionably assigned to Ulrichicrinus.
Bollandocrinus? sp. from the Keokuk Limestone might represent the first report of the genus from North America, being previously known only from the lower Carboniferous of Great Britain. Ophiurocrinus sp. from the Keokuk Limestone is the first report of this genus from the Osagean, being previously known only from the Chesterian of North America and the upper Carboniferous of Europe.