Gastropods from the Cretaceous-Palaeogene boundary in Denmark Author Hansen, Thomas text Zootaxa 2019 2019-08-12 4654 1 1 196 journal article 26049 10.11646/zootaxa.4654.1.1 9ce1d103-9234-4fbe-9544-f1c294bb8783 1175-5326 3365803 CFD82CC0-3110-472E-972B-7ADC0C523A04 Cerithium sp. Figs 23 F–H Material. MGUH 33124, MGUH 33125, MGUH 33126, and two fragmentary specimens without number located in the old collections of the Natural History Museum of Denmark . Occurrence. It ranges from the Lithified top of the Maastrichtian Tor Formation and up into the lower Danian Korsnaeb Member infilled Thalassinoides burrows in the Cerithium Limestone at Stevns Klint. Description. Protoconch unknown. Teleoconch whorls flat, separated by narrow suture located immediately abapical to keel ridge. Wide and low varices scattered unevenly on spire, the last occurring approximately opposite aperture on last whorl. Keel carrying two sharply developed ridges, adapical one only visible on last whorl. Base flattened. Aperture relatively small, strongly rounded adaxially against only slightly convex columella; inner lip well developed with strong parietal ridge forming continuation of abapical keel ridge. Columellar fold absent. Teleoconch sculpture on younger whorls consisting of weak transverse ribs crossed by spiral lirae, forming up to five weak, beaded spiral ribs. Adult teleoconch whorls nearly smooth but for fine spiral lirae and a weak spiral band of 40 to 50 tubercles per whorl adjacent to adapical suture. Growth lines slightly opisthocyrt, forming very fine and dense pattern on whorl surface, on adapical keel ridge developing into very fine and dense beading. Base covered by spiral ribs of unequal strength. Measurements. Largest specimen, MGUH 33124, 10.5 mm in diameter with a last whorl height approximating 13 mm . Remarks. Because of the flattened and weakly sculptured whorls this taxon is not a Cerithium sensu stricto , but belongs most likely to one of the many subgenera erected for this genus. Its affinity with the genus is clearly seen from the aperture with its distinctly rounded outline, strong parietal lip, nearly centrally placed columella, well developed parietal ridge and rather weakly opisthocyrt growth lines. It is distinguished from the genus Metacerithium Cossmann, 1906 by the presence of varices, the strong parietal ridge and the rather weakly forwardly reaching sinus of the basal growth lines.