Grewingkia canadensis? Horn Coral

 

These horn coral fossils appear to be Grewingkia canadensis (Billings, 1862). They were found in the Whitewater (aka Saluda) Formation of Napoleon Indiana USA. They date to the Hirnantian stage, Richmondian local stage of the Ordovician Period. The first fossil shown is just a cross section but shows a good view the septa. The second fossil does not have a visible septa but shows the more cornucopia shape of the horn coral.