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Peterjamesia circumscripta (Taylor) D.Hawksw.
 
(= Sclerophyton circumscriptum (Taylor) Zahlbr.; "Sclerophytonomyces circumscriptus"[invalid]; "Sclerophytomyces circumscriptus"[invalid])


Thallus white to pale grey, thin, areolate, scratching orange due to the contained Trentepohlia photobiont, surface scurfy with calcium oxalate crystals, thallus delimited by a black prothallus and forming mosaics, soredia absent; apothecia generally present, minute (about 0.1mm diameter), immersed in the thallus, disks black but usually white-pruinose. On coastal rock-faces, confined to dry crevices and beneath overhangs, away from direct wetting, locally frequent up the west coast, much rarer in the east. Presence of apothecia and absence of soredia separate this species from the closely allied P. sorediata, with which it may grow.

Refs: Smith et al. (2009), 688; Purvis et al. (1992), 562 (as Sclerophyton); Dobson (2005), 404 (photo, as Sclerophytonomyces); Dobson (2011), 331 (photo).

Synonymy of this species is a nasty tangle of invalidly described or named genera, incorrectly formulated names and dubious author citations following 'orthographic correction'. The situation is largely summarised by Hawksworth (2006) Lichenologist 38(2): 187-190. Listings in internet databases are variably correct.

Peterjamesia circumscripta
In crevice in seacliff (difficult to access), Bàgh a Ghallanaich, Isle of Muck (BLS meeting), August 2011


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Uploaded July 2012, last modified February 2013