Hello, 

I keep finding something with spores like Saccothecium, but not perithecioid, nor thyriothecium. Have several collections on Tamarix (intact bark of dead attached twigs), but B. Wergen seems to have collected it on stems of Ammophila as well. 
Spores ca. 13,5-16,5 × 5,4-6 um, most often 3-septate, finally up to 4-5 trasversal septa and sometimes 1 vertical in the widest segment. Sheath present. Asci 8-spored, initially pyriform becoming subglobose, IKI-, K/IKI-. 
Not sure whether it's lichenised or not. 

I believe it could be something from Arthoniales. Naevia (Arthonia) punctiformis looks similar, but has bigger spores and IKI+(r)b hymenium, N. radiata matches the spore size but differs in ascoma shape and presence of whitish thallus. A. anombrophila is amyloid. 

Does anyone know this fungus? 

Thanks a lot in advance. 
Viktorie