This is a 3-D fossil of a Conulariid from the Ordovician rocks near St. Petersburg, Russia. It is well preserved and has a bumpy detail to the surface in addition to the normal lines that decorate such shells.
I took pictures of the shell all the way around with each pic showing the specimen rotated 45 degrees to the left.
Lastly a shot down the length of the specimen showing the nearly perfect square shape.
The specimen came from the Putilovo Quarry (more famous for it's trilobites) whose rocks are middle Ordovician in age (part of the Volkhov stage in the Baltic or the Dapingian stage in the ICS timescale).