"This guide will aid the identification and recording of over 50 species of freshwater snails (gastropod molluscs) found in Britain and Ireland. It includes species found in ponds, rivers, streams, canals, brackish water and the margins of saltmarsh and lagoons.Freshwater snails play a vital role in food webs and water purification. Some indicate unspoilt or very specialised habitats, while others host unwelcome parasites, or are nuisance invaders. Updated names are used to reflect recent taxonomic research, and new maps are used to show the changing distribution of many species. Sections on field survey and conservation, drawing on many years experience, are included.Three different routes to identification are provided:- A simple key.- Comprehensive species accounts.- Pictorial index showing typical examples.These can be used separately or together. Details are also provided on dissection and the identification of juveniles, eggs and spawn. This guide aims to make accurate identification easier for beginners and experts alike." -- Provided by publisher.