Confidence: I'm as sure as I can be.
Notes: Left: Peltigera horizontalis - like the more common P. hymemina, smooth above, horizontally held fruit-bodies (apothecia). (But would be nice to see underside, confirming presence of blackish-brown veins.) Right: P. membranacea - minutely grey-pubescent above, with surface wrinkles. Need view of underside to separate from P. canina, but wrong habitat for that.