No idea what it is... but one can hope it's a cephy fossil! Looking forward to finding out what it is if any of you fossil folks can help out. It's a little bigger than a golf ball. Looks like one quarter of an ammonite but I don't know. I hope the pictures show the details well enough. The place where I work has a lot of rock on the walkways and I've been finding a lot of fossilized bi-valve shells so I've been looking very carefully lately and this was the absolute jewel so far. I actually found a completely intact bi-valve today also.