Article: Ostracod assemblages and the depositional environments of the Headon, Osborne, and Bembridge Beds (Upper Eocene) of the Hampshire Basin

Six ostracod assemblages have been recognized from the Headon-Bembridge Beds of the Hampshire Basin by the use of cluster analysis employing Jaccard and Dice Coefficients. They are thought to be salinity controlled and are comparable with Recent ostracod assemblages. Two are believed to represent a freshwater environment (0-30%o salinity), the first characterized by Candona and Cypridopsis, the second by Moenocypris. Three are believed to represent brackish environments, characterized by Cytheromorpha (3-9%o), Neocyprideis (9.0- 16.5%o), and Haplocytheridea (16.5- 35.0%o). The sixth assemblage is believed to represent a truly marine environment. Evidence for post-mortem movement of valves and for mixed assemblages is examined. The autecology of N. colwellensis (Jones) is studied, especially the relationship between salinity and size and the development of nodes; variation in carapace ornament is believed to be related to CaCO3 content of the water. Seven new species and two new subspecies are described.