Teloschistaceae Calogaya oblitterata (Caloplaca arnoldii) Growth type crustose Chemical results: K+ crimson Usually coastal on well-illuminated siliceous rocks. Forms neat patches or rosettes of orange-yellow to deep orange thallus, the marginal lobes shorter and slightly fan-shaped. Apothecia scarce, flat orange discs with a thin margin. Asci 8-spored, spores polarilocular, 8-14 x 4-7 µm with a wide septum (about or more than 1/3 of spore length). Similar: Caloplaca saxicola occurs on calcareous rocks

Caloplaca arnoldii
On chert, Portland, Dorset. February 2016