Wahlman G.P. (1992). Middle and Upper Ordovician symmetrical univalved mollusks (Monoplacophora and Bellerophontina) of the Cincinnati Arch region. United States Geological Survey Professional Paper. 1066-O: 1-213.
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Wahlman G.P.
1992
Middle and Upper Ordovician symmetrical univalved mollusks (Monoplacophora and Bellerophontina) of the Cincinnati Arch region
United States Geological Survey Professional Paper