Paleozoic species of the genus Bairdia have been critically examined and revised by use of punched cards. These species are referred to the following genera: Bairdia McCoy, Cryptobairdia n. gen., Rectobairdia n. gen., Bairdiacypris Bradfield, Fabalicypris Cooper, Orthobairdia n. gen., Pustulobairdia n. gen., Ceratobairdia Sohn, Bairdiolites Croneis and Gale, Rishona n. gen., and Bekena Gibson. Other species are referred to Basslerella? Kellett, Camdenidea Swain, Cavellina? Coryell, Haworthina Kellett, and Steusloffina Teichert. The stratigraphic range of Bairdia, as redefined, is restricted to rocks of Middle Devonian to Permian age. It is suggested that the post-Paleozoic species referred to this genus belong to other genera, several of which are listed, and some of which are still undescribed. Homonyms of Paleozoic species are renamed as follows: Bairdia egorovi (B. symmetrica Egorov, 1953), B. elongatella (B. plebia elongata Kirkby, 1859), B. girtyi (B. attenuata Girty), Cryptobairdia contractella (B. hisingeri contracta Jones and Kirkby, 1895), Orthobairdia kirki (B. compressa Geis, 1932), Rectobairdia posneri (Bairdia angulata Posner, 1951).
The following genera are discussed: Silenites Coryell and Booth, Tubulibairdia Swartz, Phanassymetria Roth, Pachydomella Ulrich, Spinobairdia Morris and Hill, and Bairdiocypris Kegel. The new family Rishoniidae is erected for Rishona n. gen. and Samarella Polenova, 1952. Reversocypris Pfibyl, 1955, is here tentatively considered a junior subjective synonym of Samarella. A new family to be named by Berdan and Sohn is discussed and illustrated by means of polished sections and radiographs.
A key to the more important genera and nine dichotomous keys to the species in these genera are presented. Some of these species are here considered nomina dubia. Misidentifications that belong to new species, except for Bairdia hassi n. sp., and B. pseudoglennensis n. sp., are not named; they are indicated by letters. Lectotypes for Orthobairdia cestriensis (Ulrich), 1891, Bekena peoki (Morey), 1935, Cryptobairdia recta (Harlton), 1929, Bairdia crassa Harlton, 1929, and Bairdia girtyi Sohn, n. name are described and illustrated. Rishona bassleri n. sp. is described and illustrated.