Orthoceras

Extinct genus of molluscs

Orthoceras, from Ancient Greek ὀρθός (orthós), meaning "straight", and κέρας (kéras), meaning "horn", is a genus of extinct nautiloid cephalopod restricted to Middle Ordovician-aged marine limestones of the Baltic States and Sweden. This genus is sometimes called Orthoceratites and misspelled as Orthocera, Orthocerus, or Orthoceros. Orthoceras was formerly thought to have had a worldwide distribution due to the genus' use as a wastebasket taxon for numerous species of conical-shelled (orthocone) nautiloids throughout the Paleozoic and Triassic.

From Wikipedia, under CC BY-SA. More on occurri.