Oncoceras

Oncoceras Temporal range: Mid -Late Ordovician
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Oncocerida
Genus:	Oncoceras Hall,1847

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.

...
Wikipedia