Limacina retroversa (Flem.) has been known in the Channel for over twenty-seven years and was several times recorded by Gough (1907) and Bygrave (1911) in the plankton reports (see Marine Biological Association, Plymouth Marine Fauna, 1931, p. 265), both from inshore and from outside. In recent years the more frequent collecting in the waters round Plymouth has shown that it may be present throughout the year, although much the most abundant in summer. Not only is it found in the outside waters but it is also often present in the Sound and even at the mouths of the estuaries.