This is the first identification work for marine and brackish water Bryozoans (“moss animals) of the Southern Bight of the North Sea. It has become a virtually complete inventory of a group of animals that has been the object of very few studies so far, but that encompasses a surprisingly large variety of species. As many as 179 species are discussed, all of which were found on beaches, in ports and in marine habitats between Cap Gris Nez (Northern France) and the Dutch-German border. The sandy substrate that is predominant in this area is usually poor in moss animal species. The fact that such a large number of species are described in this work is the result of an in-depth study of recent observations (tide mark material, specimens collected on the hard substrate of breakwaters and port structures, shells and stones near sandbanks) and the review of historical collections. The author found some 20 species in ports and on breakwaters. The Westhinder sandbank proved to be a true “moss animal paradise”, with 80 species found. And between 1998 and 2005 some 75 species were identified on objects washed ashore, of which 46 species are restricted to beached material. They are often species that are indigenous to the French and English Channel coast. Occasionally a species of tropical origin is washed ashore. The other 133 species have been found alive in this region at one time or another. Out of them, 57 are common, 56 are rare and 20 have not been found recently. In the past 15 years, 7 newcomers have immigrated with success, demonstrating that Bryozoans may well serve as indicators of climatic changes and of the introduction of exotic species facilitated by man.For convenience’s sake a double page has been created for each species: a text on the left-hand side and a set of unique photographs, made especially for this book, on the right-hand side. The photographs include a caption (in English) mentioning the abundance of the species on objects washed ashore, on hard substrate, or in historical collections. Thanks to the different determination keys in the book and a 20-30x magnifying glass it is possible to recognise most of the moss animals in the study area. We hope that this work will contribute to a better understanding of this colony-forming, undervalued group of animals.