Ostracoda and the Eocene-Oligocene boundary in north-west Europe.

The main taxonomical part is devoted to a study of the Family Cytherettidae, with the description of 49 species and subspecies belonging to the genus Cytheretta and 8 to the genus Flexus. Of these, 26 and 4 respectively are new. The type species, C. rubra Muller, is redescribed, together with l8 species and subspecies from the highest Middle Eocene and Upper Eocene of N.W. Europe, l6 from the Oligocene, and 13 from the Oligocene of Aquitaine. 38 species and subspecies are described from the Sannoisian of the Anglo-Paris Basin, including two new genera Vecticypris and Hammatocythere, one new subgenus Limnocythere (Cladarocythere), and 12 new species. The base of the Upper Eocene is defined as the base of the Bartonian, which coincides with the N. prestwichianus Band of the Hampshire Basin. The Barton Clay is correlated with the Marnes a P. ludensis in the Paris Basin, so that the underlying Sables moyens are referred to the Middle Eocene. The base of the Oligocene is taken as the base of the Rupelian; the lower part of this is the Sannoisian sub-stage. The Lattorfian is older and is placed in the Upper Eocene, while the Tongrian is in part equivalent to the Lattorfian and in part to the Sannoisian; this leads to the rejection of its use as a stage name. The term Lattorfian as used in the Tethyan province is considered to be equivalent to the Sannoisian and not the type Lattorfian, and is therefore Lower Oligocene.