Coccolithaceae
Coccolithus Schwarz, 1894
Circular to elliptical placoliths with a distal shield exhibit constant extinction, indicating a vertical optic axis relative to the microscope stage in the plan view. The proximal shield is double-tiered. In the plan view, the upper tier also shows constant extinction, similar to the distal shield. In contrast, the lower tier of the proximal shield has an inclined optic axis and exhibits length-fast (-) elongation. Additionally, the tube cycle, a permanent part of the structure, has an inclined optic axis showing length-fast (-) elongation in the plan view.
Poche, F. 1913. Das System der Protozoa. Archiv für Protistenkunde. 30: 125-321.
Schwarz, E. H. L. 1894. Coccoliths. Annals and Magazine of Natural History 14: 341-346.
