Anthoceras
Anthoceras is a genus of straight, annulated, proterocamerioceratid molluscs (Order Endocerida) from the Lower Ordovician, found in North America, North-Western Australia, and Siberia. The cross section is circular, the siphuncle moderately large, and marginal. Segments are constricted (producing concave profiles in internal molds); septal necks hemichoantici to subholochoantic (reaching halfway to almost to the previous septum); connecting rings thick. Endocones are long and slightly asymmetric. This genus is based on the phragmocone, the chambered part of the shell; the apical and apertural ends are unknown. See also
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