The Echinoid Directory
Clarkiella hemispherica (Slocum, 1909); holotype. Maastrichtian, Late Cretaceous, Pataula Creek, Clay County, USA. From P. M. Kier. 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections, 144 (3) 262 pp. (plate 21, fig. 6). Apical view.
Length of test 30 mm.