Species of the late Osagean and early Meramecian advanced cladid crinoid genera (suborder Poteriocrinina) Abrotocrinus, Aulocrinus, Cromyocrinus. Decadocrinus, Dinotocrinus, Holcocrinus, Hylodecrinus, Lanecrinus n. gen., Pachylocrinus, Parascytalocrinus n. gen., and Stinocrinus from Illinois, Indiana, Iowa, Kentucky, and Missouri are redescribed and redefined from study of type material and museum collections. Nomenclatural and systematic acts include the following: 1) Abrotocrinus cymosus Miller and Gurley, 1890a, is a valid species and not a synonym of A. coreyi (Meek and Worthen, 1869); 2) A. coreyi is a senior synonym of Poteriocrinus orestes Worthen, 1882; 3) Scaphiocrinus manus Miller and Gurley, 1890a, is assigned to Abrotocrinus; 4) Abrotocrinus granulatus n. sp. is described; 5) S. bellus Miller and Gurley, 1890a, is assigned to Aulocrinus and is a senior synonym of Aulocrinus agassizi Wachsmuth and Springer, 1897; 6) S. orbicularis Hall, 1861a, is assigned to Cromyocrinus; 7) P. latidactylus Worthen, 1882, is assigned to Dinotocrinus; 8) S. gibsoni White, 1878, is assigned to Hylodecrinus with P. nauvooensis Worthen, 1882, questionably placed in synonymy; 9) P. briareus Worthen, 1882, is assigned to Hylodecrinus and is a senior synonym of S. lacunosus Miller and Gurley, 1890a, S. boonvillensis Miller, 1891b, S. constrictus Miller, 1891a, and S. arrosus Miller and Gurley, 1893; 10) S. bonoensis Miller and Gurley, 1890a, is assigned to Hylodecrinus; 11) Hylodecrinus robustus n. sp. is described; 12) P. validus Worthen, 1882, is questionably assigned to Hylodecrinus; 13) Lanecrinus n. gen. is described and the following species are assigned to this new genus: S. halli Hall, 1861 a, S. depressus Meek and Worthen, 1870, P. milleri Wetherby, 1881, P. fountainensis Worthen, 1882, S. repertus Miller and Gurley, 1890a, and Ramulocrinus consectatus Strimple and Watkins, 1969; P. otterensis Worthen, 1882, is questionably assigned to Lanecrinus; 14) Lanecrinus depressus is the senior synonym of P. ulrichi Worthen in Miller, 1889, and S. maniformis Miller, 1892; 15) Lanecrinus repertus is the senior synonym of S. gorbyi Miller, 1891a; 16) P. asper Worthen, 1882, is assigned to Pachylocrinus and is a senior synonym of S. extensus Wachsmuth and Springer, 1886; 17) Parascytalocrinus n. gen. is described and the following species are assigned to this new genus: Poteriocrinus hamiltonensis Worthen, 1882, and Scytalocrinus validus Wachsmuth and Springer, 1897; 18) Poteriocrinites mcadamsi Meek and Worthen, 1873, is questionably placed in synonymy with Parascytalocrinus hamiltonensis; and 19) Poteriocrinus burketi Worthen, 1882, nomen dubium and Zeacrinus dubius Miller and Gurley, 1890a, are placed in Incertae Sedis.
Cromyocrinus orbicularis is the oldest species of its genus extending the range of the genus downward from the Upper to the Lower Mississippian.