Previously posted Protblastenia incrustans from marble band at Sibley Pass, 1860m, North Cascades. Weather and time limited what I could do there last month. (Previous visit in 2010 weather was even worse.) But surprised by how much on 2 small pieces of marble from August 29. Stumped by a Staurothele (see posted photos):
endolithic; surface of marble varies but seems darker than elsewhere, seems like some association with minute pits with cyanobacterea (I think) 
black perithecia, ≤o.4mm, leave pits in marble surface
involucrellum extends towards base of exciple
periphysoids present
hymenial algae almost round
asci clavate, (appearance of ocular chamber sort of, which Staurothele should lack - see one photo)
8 spores/ascus
spores become dark brown, muriform, size varies considerably - say 32-40 x 20-28 µm

Thanks Bruce. I wondered if it was an aberrant example of one of those species, but concerned particularly about it having 8 spores/ascus and for S. rupifraga the presence of involucrella.

Had used McCune 2018 “Microlichens”, Thompson 1997 “Arctic”, and Orange et al 2009 in “British”. Looked through those again now, and also looked at Thompson 1991 in Bryologist, and Wirth 2013 “Deutschlands”. Within these sources, none of the species mentioned will fit unless some characteristics are more plastic than I’m lead to believe. Getting lost searching with “Recent Literature on Lichens”, so unless you suggest more references I’m ready to throw in the towel. As “The Swamp” (as Sharon calls my room) isn’t a safe place for specimens I’ll send both to WTU Herbarium, or if of interest one to you.