THE NAMURIAN GONIATITES CRAVENOCERATOIDES BISATI HUDSON AND CT. LIRIFER N.SP.

Abstract

One of the most widely distributed and easily accessible faunas of the Namurian of Great Britain is that of the Ct. 1 nitidus zone, the middle zone of the Arnsbergian (Upper Eumorphoceras Age, E2; see Hudson 1944, Hudson and Cotton 1943 and 1945, Schmidt 1933, Demanet 1941). The zone is divided into three subzones characterised respectively by Ct. bisati (at the base), Ct. nitidus, and Ct. stellarum (Hudson 1945), species which are used as subzonal indices. Each subzone contains two or more faunal bands each with a characteristic goniatite fauna. The forms in these faunas are, however, not easy to identify specifically since they usually occur as crushed specimens in shale, whereas most of the species that occur in the zone have been founded on uncrushed specimens such as occur in the occasional bullion (clayironstone nodule); comparison is therefore difficult. Even when the types are crushed-shale specimens the illustration of the species has usually been inadequate and identification is no easier. The result of this lack of definition is that it has not been possible either to allocate certain forms from this zone to the known species or to use them for the foundation of new ones. Two of these forms occur in the lowest part of the Ct. nitidus zone and have been respectively and variously referred to as Ct. aff. edalensis and Ct. aff. stellarum. Since they are of stratigraphical importance, an attempt has been made to give them specific definition. Specimens have been compared with the types and, ...