Historical reference: Do not rely on this information. It is very old. About this collection
Trigonellites, a genus once proposed for some calcareous plates found in the Cretaceous and Oolitic rocks, in association with Ammonites. They are now known to have been parts of Ammonites, formed by calcification of part of the "hood," and used to close the mouth of the shell when the animal is withdrawn into it.