A checklist of Australian marine Cenozoic Mollusca Author Darragh, Thomas A. text Memoirs of Museum Victoria 2024 2024-08-23 83 37 206 https://doi.org/10.24199/j.mmv.2024.83.02 journal article 10.24199/j.mmv.2024.83.02 1447-2554 14704472 Calliostoma semiornata Chapman, 1926 Calliostoma semiornata Chapman, 1926: 133 , pl. 10, figs 5, 6. Distribution . Otway Basin: Muddy Creek Formation ( type ). Gippsland Basin: Gippsland Limestone. Age : middle Miocene.