This is a cluster of poorly preserved spiriferid brachiopods. They are found in clusters on occasion.
As to what type (genus) they are, I have no clue. There are lots of types and these ones are too worn to see any of the genus specific traits.
I attached a picture tracing them out on your image, and also an image of a similar cluster of better preserved ones from a different local.
The other side of it, it looks like that could be a piece of brachiopod impression (the ridges area). The rest of it may have a bryozoan colony growing on it, those tiny little bumpy thingys (to be technical).