Prinsiaceae
Prinsius Hay & Mohler, 1967
The circular to elliptical placolith comprises a single-tiered distal shield, a double-tiered proximal shield, a central structure and a double tube cycle visible distally.
Optical Properties: In the plan view, the distal shield and the proximal shield’s upper tier exhibit constant extinction because their optic axis is vertical relative to the microscope stage. The tube cycle and the lower tier of the proximal shield display inclined extinction lines. The tube cycle shows length-slow (+) elongation, whereas the lower tier of the proximal shield shows length-fast (-) elongation.
Hay, W. W. & Mohler, H. P. 1967, Calcareous nannoplankton from Early Tertiary rocks at Point Labau, France and Paleocene-Early Eocene correlations. Journal of Paleontology 41(6): 1505-1541.
