Thanks for the link baza although they are quoting the same sources that I consulted, ie the excavations in the 1920s. I just think that it should be re-assessed in the light of our present knowledge. I'm not an expert in this area of possible carvings so the more opinions (of those who have seen it) the better.
My own feelings?.......Some marks are surely natural but what process (erosion or lost fossils[?]) could have caused the peculiar parallel wavy lines?