Littoral gastropods of the families Littorinidae and Muricidae are well studied compared to most marine taxa, yet there remain many basic problems concerning their taxonomy, ecology and evolutionary biology. In other words, we know these snails well enough to realize just how little we really know about them. This awareness prompted the First European Meeting on Littorinid Biology held at the British Museum in London on 26th November 1986, and the discussion continued through the Second Meeting on Littorinid Biology, held at the Tjarno Marine Biological Laboratory, Sweden, from 4th to 8th July 1988. During the Tjiirno meeting, it was agreed to have a third meeting at Dale, Pembroke shire, U.K. in 1990. Twenty-two people attended the Tjarno meeting, and a further ten contributed as co-authors to the papers that were presented. These covered research in progress in a broad range of topics, and geo­ graphical areas. Unfortunately, Cesare Sacchi and Domenico Voltolina, as well as Elisabeth Boulding were not able to attend the meeting in person, but their contributions were ably presented by David Reid and Richard Palmer, respectively. We also regret that one of us, C.E., and several of our Russian colleagues, did not have the opportunity to come.

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1. A cladistic phylogeny of the genus Littorina (Gastropoda): implications for evolution of reproductive strategies and for classification.- 2. Distribution of the species of rough periwinkle (Littorina) in Great Britain.- 3. Estimating the phylogeny of the mollusc Littorina saxatilis (Olivi) from enzyme data: methodological considerations.- 4. Are the opposing selection pressures on exposed and protected shores sufficient to maintain genetic differentiation between gastropod populations with high intermigration rates?.- 5. Biochemical genetic variation in the genus Littorina (Prosobranchia: Mollusca).- 6. Littorina neglecta Bean, a morphological form within the variable species Littorina saxatilus (Olivi)?.- 7. Genetic variation within Littorina saxatilis (Olivi) and Littorina neglecta Bean: is L. neglecta a good species?.- 8. Rapid colonization of Belgian breakwaters by the direct developer, Littorina saxatilis (Olivi) (Prosobranchia, Mollusca).- 9. Hybridisation in the Littorina saxatilis species complex (Prosobranchia: Mollusca).- 10. Scraping a living: a review of littorinid grazing.- 11. Littorina mariae - a factor structuring low shore communities?.- 12. Field observations on the feeding habits of Littorina scutulata Gould and L. sitkana Philippi (Gastropoda, Prosobranchia) of southern Vancouver Island (British Columbia, Canada).- 13. Effect of crab effluent and scent of damaged conspecifics on feeding, growth, and shell morphology of the Atlantic dogwhelk Nucella lapillus.- 14. The relationship between flat periwinkle life histories and digenean infections.- 15. Feeding behaviour in Littorina littorea: a study of the effects of ingestive conditioning and previous dietary history on food preference and rates of consumption.- 16. Shell microstructure and mineralogy of the Littorinidae: ecological and evolutionary significance.- 17. Differences in shell properties between morphs of Littoraria pallescens.- 18. Adaptive and non-adaptive variation in two species of rough periwinkle (Littorina) on British shores.- 19. Distribution, abundance and shell morphology of Littorina saxatilis (Olivi) and Littorina arcana Hannaford Ellis at Robin Hood's Bay, North Yorkshire.- 20. Thermal tolerance, evaporative water loss, air-water oxygen consumption and zonation of intertidal prosobranchs: a new synthesis.- 21. Mate discrimination in Littorina littorea (L.) and L. saxatilis (Olivi) (Mollusca: Prosobranchia).- 22. Epilogue.- Index of genera and species.- General index.