Psiloceras
planorbis J. Sowerby 1824
Somerset Coast
Family PSILOCERATIDAE Hyatt, 1867
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Psiloceras
planorbis J. Sowerby 1824
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Somerset Coast
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Family PSILOCERATIDAE Hyatt, 1867
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| A Zone and Subzone ammonite of the Hettangian Stage. | |
| Small compressed planulates, smooth, unribbed. First ammonite to appear in the geological record. | |
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