Article: On the nautiloid Leurocycloceras from the Ludlovian of Wales and the Welsh Borderland

Wahlenberg's species Orthoceratites imbricatus is discussed and considered a nomen dubium. The characteristic isolated cameral moulds from the upper part of the Ludlovian (Silurian) of Wales and the Welsh Borderland, which have been commonly referred to this species or to Orthoceras marloense Phillips, are assigned to the genus Leurocycloceras Foerste, under the new specific name L. whitcliffense. The latter species is fully described and problems of the preservation and interpretation of the moulds are discussed. It is concluded that Leurocycloceras provides decisive evidence for the organic origin of cameral deposits.