It’s in the genus Peltigera
Cheers, Chris
[attachment=0]Picture.jpg
I note JennyS hasn’t commented, which is probably a comment in itself 
From your first photograph the upper surface looks to be smooth (i.e. not tomentose or felted) with up-turned edges and a pale underside. Unfortunately the photograph of the underside is not sufficiently defined to make a confident identification. However, if the veins are flattened and pale or tan with pale interstices and the rhizines are simple (may have tufted ends) and widely spaced, it is probably P. hymenina
When trying to identify Peltigera it is important to look at both surfaces.
I would recommend looking at Jenny’s sites (
Hope this helps
Christine
It appears to have a very fine, pale tomentum which is densest at the thallus margins (at X20). The veins are flattened and pale with pale interstices, in most cases almost indiscernible but in a few cases slightly darker, tan coloured. Most rhizines are simple but some have tufted ends (from about 2/3rds from base).
That probably doesn’t clear it up any. It does have a rather attractive lichenicolous fungus growing on it as well.
More interesting is any lichenicolous fungi – got any shots/details of that?
Cheers
Ken
Your suggestion of orange spots fits with Marchandiomyces corralinus/aurantiacus, usually on Parmelia sp or, but usually on Physcia sp, Illosporiopsis christiansenii – neither is known to me colonising Peltigera………but I don’t know everything, there might be something!
Does this help?
Cheers
Ken
http://www.dorsetnature.co.uk/pages-lichen/lch-346.htmlhttp://www.dorsetnature.co.uk/pages-lichen/lch-346.html
Illosporiopsis is pink rather than orange, and like Marchandiomyces not known on Peltigera’s – but there are plenty of others that are and if you can get a look at the spores that would help
Marchandiomyces corallinus
The substrate is a corner of the lichen shown in the first photograph.
