Recognition of the marine gastropod Caecum tumidum Carpenter, 1858 (Caenogastropoda, Truncatelloidea) in the Pliocene of the North Sea Basin

In 1858 Carpenter described the fossil “Caecum trachea” sensu Wood (1842, 1848) from the Pliocene British Crag Mollusca as new to science and named it Caecum tumidum. A lectotype is selected to stabilize the species. C. tumidum appears also present in the Pliocene of Belgium and The Netherlands. As C. tumidum until recently has been mistaken for Caecum trachea (Montagu, 1803) = Caecum imperforatum (Kanmacher, 1798) as well as for Caecum mammillatum Wood, 1848, diagnostic characters and photographs are presented to distinguish the three species.