The Occasional fossil

This is not one fossil but a whole bunch. Back when this rock was sediment there were all sorts of organisms living in it. As they burrowed through the sediment they made tunnels which, themselves, filled with sediment. When the sediment turned to rock the fluid carry the cementing agent was able to penetrate the relatively un packed filled in tunnel better than the surrounding sediment so as the rock weathers and erodes the tunnels "stick out". Remember from an earlier post these are trace fossils.