Orthoceras
Pronunciation : Or*thoc"e*ras
Part of Speech : n.
Etymology : [NL., fr. Gr. (Paleon.)
Definition : Defn: An extinct genus of Paleozoic Cephalopoda, having a long, straight, conical shell. The interior is divided into numerous chambers by transverse septa.
Source : Webster's Unabridged Dictionary, 1913