Article: Evolution of the charophyte floras in the Upper Eocene and Lower Oligocene of the Isle of Wight

The distribution of charophyte gyrogonites in the Headon, Osborne, and Bembridge Beds is analysed. The flora, including a new species, Nitellopsis (Tectochara) latispira, is described. It is considered that transitional forms in the genera Psilochara and Harrisichara constitute examples of evolution in Palaeogene genera. The strati-graphical importance of Sphaerochara subglobosa (Groves) Horn af Rantzien, which extends from the Upper Headon to the Lower Hamstead Beds, is discussed. It is confirmed that the position of the Eocene-Oligocene boundary that most closely agrees with the charophyte distribution is that situated at the Middle Headon Beds.