Rhizocarpon lavatum?

It doesn't take much effort to determine a Rhizocarpon but getting to species level is a lot more difficult. This one wouldn't key out so I instead went with the closest match. No idea what the difference between muriform, submuriform and eumuriform is and no explanation in the book. Perhaps it would have been easier to reach an ID had I have known. I've put the details here to come back in time and re-evaluate:

Spores: muriform (or could be submuriform or eumuriform) 25x11.25µm turning brown when mature.
Ascus: 120µm
hypothecium: brown
hymenium: colourless
epithecium: brown
apothecia: 0.8mm
habitat: siliceous rocks near stream

Pos Rhizocarpon lavatum

Caloplaca from Brecon Beacons 25th March

Found on 25th March 2016 on a gate post this Caloplaca was not found to be identifiable with my level of expertise currently. A shortlist was drawn up using apothecia size (1mm) and habitat giving Caloplaca citrina as the best guess. Both the thallus and apothecia are K+ purple eliminating C. virescens and C.cerina. Apothecia colour elimnated herbidella. There were few polaricula spores the largest measured 15x4.5µm. Some of the paraphyses had swollen tips measuring 3.75µm