Loeblich, A. R., Tappan, H. N., 1987: Foraminiferal genera and their classification. Van Nostrand, Reinhold Co. New York 1728 pp. Plate 272, Fig. 7: U. Carboniferous (U. Bashkirian), Penzenskaya Oblast. Axial section, x 35 (from Rauzer-Chernousouva and Fursenko, 1959). courtesy of Michael Hesemann https://foraminifera.eu
