1946—Cushman, Joseph A. (1946). Upper Cretaceous Framinifera of the Gulf Coastal Region of the United States and Adjacent Areas. Professional Paper 206. Washington, D. C.: U. S. Department of the Interior, Geological Survey. p. 70 – via Google Books. The deck, which is not far below the aperture, has a narrow indentation on the abapical side and a wider indentation on the adapical side.
Source: wiktionary