. Bulletin of the British Museum (Natural History), Geology. 166 BRITISH CRETACEOUS GASTROPODS influence on the shell's appearance are adequate diagnostic features to separate this species from others that have been described. The lack of plications on the columella might be construed as uncharacteristic of Orthochetus, yet, Wrigley (1940 : II & 12) mentioned a number of instances in Eocene species where this feature is obscured by a reflected columella border. Its diagnostic features distinguish 0. hantoniensis from the two Maastrichtian species mentioned by Cossmann (1906 : 97) Cerithium
. Bulletin of the British Museum (Natural History), Geology. 166 BRITISH CRETACEOUS GASTROPODS influence on the shell's appearance are adequate diagnostic features to separate this species from others that have been described. The lack of plications on the columella might be construed as uncharacteristic of Orthochetus, yet, Wrigley (1940 : II & 12) mentioned a number of instances in Eocene species where this feature is obscured by a reflected columella border. Its diagnostic features distinguish 0. hantoniensis from the two Maastrichtian species mentioned by Cossmann (1906 : 97) Cerithium tectiforme Binkhorst (1861: 24 pi. I figs 3a-c) from Limbourg and 0. mapeulensis Douville (1904 : 303 pi. 41 fig. 12) from Kouh Mapeul, Persia. The ornament of both these Maastrichtian species is more reticulate, due to the presence of smaller and more numerous axial ribs. Although both 0. hantoniensis and 0. tediformis have three primary spiral cords, the presence of secondary spirals in the former and of tubercles in the latter assist in separating the two species. Douville (1904 : 303) referred to Orthochetus as an ancient group and quoted the occurrence in the Chalk of Cerithium cribriforme Zekeli (1852 : pi. 20, figs 2 & 2') as evidence. In many respects, this turreted species is very like 0. hantoniensis,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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