I agree with Larry. Most crinoid calyxes are preserved and seen side on, but if one happened to land head side down, this pattern very much resembles the image seen (and rotated a bit) at
http://www.geo.arizona.edu/geo3xx/geo30 ... echin.html
under subphylum Crinoza.
Another thought: it could be a crinoid holdfast, seen from below. Obviously the fossil is worse for wear because of the cave solutioning. The holdfast is the 'foot' of the animal, and what binds the juveniles to the rocks below. Some are simple discs, and some look very much like above ground tree roots spreading in all directions.
Google crinoid holdfasts and use a little imagination to reorient them. Or pretend you are a mole looking up at the pattern of main branching tree roots.
Actually, I'm willing to bet $5 that this is a crinoid holdfast-- not $20 or $2000, but I'd lay about 60% odds that's what you're looking at, assuming the age of the rock is appropriate: Ordovician through Pennsylvanian. Some crinoids still exist, but the end of the Pennsylvanian did many of them in.