from the GNU version of the Collaborative International Dictionary of English
- n. An extinct genus of Paleozoic Cephalopoda, having a long, straight, conical shell. The interior is divided into numerous chambers by transverse septa.
from The Century Dictionary and Cyclopedia
- n. The typical genus of Orthoceratidæ, having the shell straight or but slightly curved. The species are very numerous, ranging from the Silurian to the Liassic. Also Orthoceratites, Orthocerus.
Sorry, no etymologies found.