This image is of a Grewingkia canadensis (Billings, 1862) horn coral fossil with some borings. It was found in the area of Cincinnati Ohio USA. The fossil dates to the Ordovician Period.

Picture taken at Museo di Geologia e Paleontologia Florence Italy (Università degli Studi di Firenze) in August 2024. The image below is of another horn coral fossil which might have a piece of a Cryptolithus cephalon trilobite.