This rock is full of fossils but the one that made me keep it was the impression of a Cornellites fasiculata pelecypod. The detail of the mold is really nice but there is a little "window" in the mold that shows evidence of an encrusting bryozoan that had colonized the shell.
This is the whole rock with the impression near the bottom. The rounded object just above it (and casting the shadow) is the pygidium of a Dipleura dekayi trilobite.
When you look into the shadowed area you can see the "window
Here is a closer view and the cool thing is that you can see the clam shell, the base of the bryozoan and what looks like a worm tube that may have been on the shell before the bryozoan. The undulating shape of the bryozoan makes me think it could be a Leptotrypella species.
This fossil came from the Panther Mountain formation (Devonian, Givetian stage) at Cole Hill Rd., Madison County, NY