Helicosphaera prolixa Bown & Newsam, 2017
Bown, P. R. & Newsam, C., (2017): Calcareous nannofossils from the Eocene North Atlantic Ocean (IODP Expedition 342 Sites U1403–1411). - Journal of Nannoplankton Research. 37(1): 25-60.
Helicosphaera prolixa
Bown & Newsam, 2017
Middle Eocene