Litulites lituus
Nautiloid
Ordovician
Orthoceras Limestone
Isle of Oeland, Sweden

81mm nautiloid on 114mm matrix.

Cephalopod.

Lituites is a genus of extinct nautiloid (cephalopod) known from the Ordovician to Silurian of Europe, China, and Argentina.  It had a planospiral shell that straightened out and extended to a considerable length relative to the size of the coiled end.