The subject of this study are deep water agglutinated assemblages with an increased abundance of Spiroplectammina spectabilis (Grzybowski) and their biostratigraphic utility. Qualitative and quantitative observations of foraminiferal assemblages indicate that, in the Outer Carpathians, Spiroplectammina spectabilis acme assemblages occur within a consistent Middle Eocene interval (the Reticulophragmium amplectens and “Ammodiscus” latus zones) and may be applied as a biostratigraphic tool. In general, the proportion of Spiroplectammina spectabilis varies from 8% to 22%, with maximum values reaching 42%. The Spiroplectammina spectabilis acme has been recognized along the southeastern margin of the Outer Carpathians, within deposits of the Silesian, Skole (Skyba), Subsilesian, Dukla, Boryslav-Pokuttya, and Tarcau nappes, which represent sediments of the marginal part of the Tethys, known as the Silesian-Moldavidic Basin. It occurs mainly in thin-bedded turbidites dominated by gray and green mudstones, deposited in bathyal environments with a continuous supply of organic matter. Beyond the Carpathians, the Eocene Spiroplectammina spectabilis acme is also known from the deep Labrador Sea and from the Contessa Highway section in Italy.