 The paper describes the new species Stomiosferena baki spnov, which is the third species in the genus Stomiosferena, found in upper Cretaceous white chalk at Dubivsi section near Halic in western Ukraine. It has an asymmetrical oval test with a two-layered calcareous test, yellowish to brownish color in plain polarized light, and one narrow aperture. The species differs from other Stomiosferena species by its cis-shape, cis-size, layers thickness, structure of outer layer and width of aperture, and is likely the non-defined species described by NOAC in 1974. This article was authored by Agnieszka Sierge.