Nautiloidea, Dawsonoceratidae, Dawsonoceras americanum,  (Foord 1888)

Rochester shale

Middleport, New York

Silurian, Sheinwoodian 430.5 ±0.7 - 433.4 ±0.8 Mya

Specimen with matrix is 39 mm x 29 mm x 25 mm