Something for the Nature Table.

Taking myself back to Primary School I remember the "Nature Table" where all class mates were invited to bring items in to add to the collection displayed which would spark identity,  discussion, enquiry and learning etc. 
My item today came from the beach and appears to be an oyster shell (one half I guess) with a half cockle or winkle shell embedded in it.  The oyster shell appears to have grown around it.
I may be going quietly mad - not sure yet.