Orthoceras is an extinct cephalopod related to the modern squid, octopus, and Nautilus. They lived 500-200 million years ago. As they grew, a septa (horizontal line) grew as a diving wall to separate the old chamber and new. The siphuncle is a lone line down the middle and is a tube that could be filled with air for buoyancy or push the air out for jet propulsion. Ammonites and Nautiluses have these for the same function.

Will range in size, approximately 3 inches long.

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