Limestone concretions.

Sunderland has unusual limestone concretions. I walk past this wall regularly and I am always looking for the unusual stones. People think they are fossilised sea creatures but they are not. They are naturally occurring patterns in the rock that were created when the rocks were formed. 
 My favourite to look for is the cannonball limestone, but they have a lot of names to describe the patterns e.g. feather, cobweb, herringbone etc.
I have blipped them before. 
If you are interested the other blip was of a geology walk I did and is here.https://www.blipfoto.com/entry/2777580894578280389