Fangs for the memory

I dog-walked down into the woods. Not really a walk for either of us: she scampers off as I scramble down through hazel and holly and oak.
The river below, recently rain-swollen, was fringed with mud and detritus that needed careful footwork (by me, not her) but I was delighted to find that the mossy boulders on edge of the wood had, as I hoped, their full complement of dog lichen (Peltigera) which grows here in a profusion I rarely see elsewhere.
These leathery flaps with a smooth grey surface and frilly white edges fan across the stones like crusts of old oil paint. The underside is a mass of tiny, soft, fang-like spikes (better seen in the extra) which give the lichen its common name. 
There are many species and I'm not sure which one this is but I'm glad I remembered to go and look for it. The dog has her own business to attend to  but we re-united to trudge home. I attach her lead to give me a pull up the slope.