Oncoceras is a genus of oncocerids, family Oncoceratidae from the middle and upper Ordovician of North America and Europe.

The shell, or conch, of Oncoceras is relatively short, a curved, compressed brevicone with a maximum width in the phragmocone just behind the body chamber, narrowing toward the aperture.

The siphuncle is small, necks recurved.

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