Subprionocyclus neptuni Zone
Base: The base of the zone is defined by the first appearance of the index species (Gale, 1996).
Correlation: The presumably correlative lower part of this zone was described by Wright & Kennedy (1981). The zone equates with the upper T. lata and S. plana zones of the standard macrofossil zonal scheme.
Occurrence: The zone has been recognised in southern England, Hertfordshire and Berkshire (Gale, 1996).