The Geinitzinidae is a family of Foraminifera (Protista) from the late Paleozoic (U Dev. - U Perm) included in the Fusulinida that comprises genera characterized by unserial tests (chambers arranged in a single row, or line, in which walls are double layered. The outer layer is of light colored hyaline (glassy) radial calcite. The inner layer is a dark, secreted, microgranular calcite.