Phragmocone
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The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae.
Cutaway of a nautilus shell showing the chambers
Actinoceras
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Actinoceras is a genus of extinct cephalopod that lived from the middle Ordovician to the Early Silurian. It is the type genus of the Actinoceratidae, a family of nautiloids that thrived in the waters
Actinoceras sp. at the Royal Tyrrell Museum
The holotype of Actinoceras beloitense