Distribution of the species of rough periwinkle (Littorina) in Great Britain

The status of the four currently recognised species in the Littorina saxatilis species-complex, i.e. Littorina nigrolineata Gray, L. arcana Hannaford Ellis, L. saxatilis (Olivi) and L. neglecta Bean is reviewed briefly, with notes on their characteristic features and location on the shore. Since the taxonomy of these rough periwinkles has only become stable relatively recently much of the previously published information on distribution is of little or no use. In this paper their distribution around the coastline of England and Wales (with some notes on Scotland) is described and discussed. L. saxatilis is found in a wide range of habitats from exposed peninsulas to estuaries on all shores where there is a suitable rocky or stony substrate; also in salt marsh pools. L. arcana has a more restricted distribution and is notably absent along much of the south English coast, central Cardigan Bay and possibly northern Scotland; it is not found in estuaries. L. nigrolineata has an even more restricted distribution, although it occurs both on exposed coasts and in estuaries; it has only been found by us in one locality on the east coast. L. neglecta is probably fairly widely distributed but we have few details so far. The implications of the different patterns of distribution are discussed.