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THE ESSEX NATURALIST
P. tenella (Scop.) DC. em. Bitt.
Scarce on asbestos-cement and sandstone. 51/68, 69.
Sandstone gravestone, St Mary's Church, Little Burstead (1973, IMH);
corrugated asbestos-cement roofs, disused barracks, Langdon Hills (1974,
PME-B).
Physconia grisea (Lam.) Poelt
Frequent on limestone; scarce on asbestos-cement and concrete. 51/69,
78, 79.
Particularly associated with Physcia spp. on the tops of limestone head-
stones in churchyards.
Platismatia glauca (L.) Culb. & Culb.
Rare on Salix. 52/70.
Trunks of Salix beside stream, Galleywood Common (1972, IMH).
Protoblastenia rupestris (Scop.) Steiner
Rare on concrete. 51/69.
Concrete bridge over stream, Hutton (1971, PME-B).
Rinodina exigua (Ach.) Gray
Very rare on Salix. 51/68.
On decorticate parts of old Salix stump, Westley Heights, Langdon
Hills (1974, PME-B).
R. subexigua (Nyl.) Oliv.
Frequent on concrete, mortar, asbestos-cement and limestone. 51/68, 69.
A nitrophilous species, often found on bird-perching stones e.g. the tips
of concrete posts.
Sarcogyne regularis Korb.
Occasional on concrete and limestone. 51/69.
Concrete bridge over stream, Hutton (1971, PME-B); on concrete part
of barn, Norsey Farm, Billericay (1973, PME-B); limestone wall of All
Saints' Church, Hutton (1974, PME-B); limestone gravestone, Con-
gregational Church, Billericay (1974, PME-B).
Trapelia coarctata (Turn. ex Sm.) Choisy
Occasional on brick and sandstone. 51/69.
Brick bridge over stream and sandstone railway arches, Hutton (1971,
PME-B); brick gravestone and walls in All Saints' churchyard, Hutton
(1972, PME-B); brick walls of old Kale beds, Norsey Farm, Billericay
(1973, PME-B).
Verrucaria hochstetteri Fr.
Scarce on limestone. 51/69.
Limestone gravestone, Congregational Church, Billericay (1974,
PME-B); limestone wall of All Saints' Church, Hutton (1974, PME-B).