A description of the London Clay serpulid Rotularia bognoriensis (Mant.), its apical growth, the structure of its tube, its position of life and the origin of its sinistral forms and deformations, with a discussion of its affinities and nomenclature. The English Eocene Sclerostyla, their opercula and their living representative. Turbinia and other extinct serpulids with completely calcareous opercula. Eocene Protula and Ditrupa described . The distinctive characters of serpulid tubes investigated.