Sequences of calcareous slope and spring deposits (mainly tufa) are described from two localities in Kent (Folkestone and Wateringbury). They contain rich faunas of terrestrial Mollusca, allowing a detailed reconstruction of the local environments. The faunal changes also reveal an underlying common pattern, ascribed largely to the effects of climate and migration. Eight biostratigraphical assemblage zones are proposed, applicable to deposits of this general character in the area of southern England. The base of each zone is defined as follows: zone y first appearance of a molluscan fauna, dominantly of
Pupilla, Vallonia
and
Vitrina
; zone z expansion of
Abida
and
Trichia
; zone a decline of
Pupilla
, appearance of
Carychium
and
Aegopinella
; zone b expansion of
Carychium
and
Aegopinella
, occurrence of
Discus ruderatus
; zone c expansion of
Discus rotundatus
, suppression of
Discus ruderatus
; zone d expansion of
Oxychilus cellarius
; zone e re-expansion of
Vallonia
; zone f appearance of
Helix aspersa
. Botanical evidence (pollen and seeds) and some radiocarbon dates allow a partial correlation of the zones with the standard Godwin pollen zones of the Late Devensian (late-glacial) and the Flandrian.