Varolia cistula Bown 2005d
These are consistent with the typical optical characteristics observed in the genus Varolia.
The holococcolith features a crystalline-high wall with a modified square or rectangular shape, depending on the degree of tilting around the central void area. Typically, one side of the wall is more convex than the others, creating an asymmetrical appearance.
Bown, P. R. 2005d. Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research 27(1): 21-95.