Specimens of the Late Mississippian productoid genera Inflatia and Keokukia from northeastern Oklahoma and northwestern Arkansas, collected from the Boone and “Moorefield” Formations, Hindsville Limestone, and Fayetteville Shale, display morphologic similarities and differences that delineate species and determine their biostratigraphic ranges. Generic assignments are based primarily on internal characters. Systematic descriptions include seven species of Inflatia Muir-Wood and Cooper: Productus inflatus McChesney (the type species), P. cherokeensis Drake, P. clydensis Girty (figured herein for the first time and for which a lectotype is designated), four new species of Inflatia (I. cooperi, I. gracilis, I. pusilla, and I.? succincta), and one species of Keokukia (the type species for the genus, K. sulcata Carter). Also proposed and described is a new genus, Adairia, with its type species Productus (Marginifera) adairensis Drake. All these species of Inflatia, Keokukia, and Adairia have biostratigraphically restricted ranges within the Meramecian and Chesterian sequence in the Ozark region.