Description Loeblich, A. R., Tappan, H. N., 1987: Foraminiferal genera and their classification. Van Nostrand, Reinhold Co. New York 1728 pp. Plate 189, Figs. 3-4: Oligocene, Alazan Formation, Mexico. Type species of Alvarezina Bermúdez and Rivero. Side and edge views, x 60 (from Nuttall, 1932).