Calcivertellinae

Cushman, J. A.; Waters, J. A. (1928). Some Foraminifera from the Pennsylvanian and Permian of Texas. Contributions from the Cushman Laboratory for Foraminiferal Research. 4(2): 31-55., available online at https://cushmanfoundation.allenpress.com/Portals/_default/files/pubarchive/cclfr/4cclfr2.pdf page(s): p. 48 pl. 6 fig. 7