The book brings together all known information on the species of the nformal group 'Lower Heterobranchia' distributed along the Turkish coasts and includes 115 species belonging to 37 genera of the families Architectonicidae, Mathildidae, Omalogyridae, Cornirostridae, Hyalogyrinidae, Pyramidellidae, Amathinidae, Murchisonellidae, Graphididae, Acteonidae and Ringiculinidae. The species dealing with herein have been photographed by the author, and some information on their distributional and ecological features are presented.