I appreciate this could be a piece of rock but there does appear to be symmetry with pronounced geometric ridge details on both internal and external curves. It certainly appears to me as a fossiled claw, spine or tooth.
The more I look at this , the more I'm convinced its a fossiled claw, tooth or spine! It was collected yesterday in East Sussex. it is clearly Sickle shaped, tapering and 15.5cm in length. It appears to have a defined outer shell and an inside core, there are numererous textures on its outside faces including hollow pore like, old leather and what look to me to be bite/gouge/scratch marks?