Oysters?

On our recent visit to Whitby, we drove along the coast to Sandsend. It was beginning to get dark, but I took this photograph as a souvenir of the beach. Lewis Carroll supposedly found his inspiration for 'The Walrus and the Carpenter' during a stroll along the foreshore. Does anyone know the source for this supposition? We missed the Roman Signal Station at Goldsborough, just a little further north: we must explore this on a future occasion.