A survey of Pennine sites apparently suitable for Abida secale in August 1974 revealed that A. secale is almost completely restricted to sites west of the Pennine watershed. Sites were categorized as (a) open, (b) with occasional trees or bushes, and (e) wooded. In the west where both species live, Clausilia dubia lives in wooded sites while A. secale occupies open sites. In the east, however, C. dubia becomes abundant in open sites where A. secale is absent. Neither microclimatic differences at the sites, nor inter-specific competition seems to explain this distribution.