What the...? What is this?

[ByronNWT]

This “fossil?” Confuses me. Is it even a fossil? The shape throws me off makes me think its artificial but i found it in the middle of nowhere on rocky river shore. Geological? 

[ByronNWT]

Total piece size 2-1/4” wide 3” long 1-1/2” deep.

[fossilcrazy]

Looks like a Brevicone Cephalopod.

[ByronNWT]

Acleistoceratidae? devonian.

[ByronNWT]

* genus Acleistoceras

[JimB88]

Looks like part of an isotelus trilo to me, but I could be wrong.

[ByronNWT]

Formation is devonian i think isotelus was long gone.