I figured it was a mollusk, but my knowledge of such is very limited. I have made a shot in the dark that it is Gryphea? But I am unsure if it would even fit the time period (Miocene) or the location of the Astoria Formation in Oregon. Please put any guesses you may have even if they seem totally wrong.
By the way Its glossy texture is due to a coating i put on it due to its tendency to flake off pieces, not the fossils look.