- An extinct genus of Paleozoic Cephalopoda, having a long, straight, conical shell. The interior is split into many chambers by transverse septa.
- the conventional genus of Orthoceratidæ, obtaining the shell straight or but slightly curved. The species are particularly many, which range from the Silurian toward Liassic. Also Orthoceratites, Orthocerus.
Sentence for "orthoceras"
- Some of the ammonites, which belonged…
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