LECANORA] LECANORACEE 263 
Easicc. Dicks. Hort. Sicc. fase. vii. n. 25; Larb. Lich. Hb. 
n. 50. 
Owing to the presence of cephalodia placed in Sqwamaria subg. 
Placopsis by Nylander in Ann. Sci. Nat. xv. p. 376 (1861). Lecanora 
subg. Placopsis Cromb. Monogr. i. p. 355 (1894). 
Often sterile, but well marked by the prominent cephalodia, 
which contain Stigonema and Nostoc alge. A young stage with 
scattered thalli and small cephalodia has been described as f. dispersa 
Cromb. in Grevillea i. p. 171 (1873). 
Hab. On siliceous rocks in maritime, upland and_ subalpine 
districts.— Distr. In the rocky or hilly regions of England, Scotland 
and Ireland.—B. M. St. Austell, Cornwall ; Cader Idris, Dolgelly and 
Llyn Bodlyn, Merioneth ; Nant Ffrancon and Cwm Glyders, Carnar- 
vonshire; Egglestone and Teesdale, Durham; near Kendal, West- 
moreland; Knock Morton Screes, Cumberland, New Galloway. 
Kirkeudbrightshire ; Loch Awe, Argyll ; Craig Calliach, Ben Chaluna, 
Ben Lawers and Craig Tulloch, Perthshire; Clova and Canlochan, 
Forfarshire; Glen Cluny, Invercauld and Glen Caudlic, Braemar, 
Aberdeenshire; Rothiemurchus, Ben Nevis and Fort Augustus, 
Invernessshire; Hills of Applecross, Rossshire; Dunkerron and 
Connor Cliffs, Dingle, Kerry; Letterfrack and Recess, Connemara, 
Galway ; Belclare and Clare Island, Mayo; Carnlough, Antrim. 
7. L. muralis Scher. Enum. Lich. p. 66 (1850).—Thallus 
normally orbicular, often wide-spreading, pale-brownish or 
greenish-straw-coloured, appressed, imbricate or areolate-crus- 
taceous in the centre, radiate-syuamulose at the circumference, 
the squamules contiguous, narrow or rather broad, flat or 
subplicate, crenate at the apices, sometimes white at the margins. 
Apothecia up to 2 mm. in diameter, crowded, generally plane, the 
dise yellowish-brown, the thalline margin thin, flexuous or 
crenulate, rather light-coloured ; paraphyses irregular, slightly 
thicker upwards, the epithecium a brownish grumous layer ; 
spores ellipsoid, 9-16 » long, 4—7 » thick.—L. saxicola Acb. Lich. 
Univ. p. 431 (1810) ; Tayl. in Mackay FI. Hib. ii. p. 140; Cromb. 
Monogr. i. p. 353 (incl. subsp. albomarginata) ; var. albomarginata 
Nyl. ex. Norrl. in Sillsk. Faun. & Fl. Fenn. Forh. viii. p. 181 
(1871). Lichen muralis Schreb. Spicil. Fl. Lips. p. 130 (1771), 
fide Arn. in Flora Ixvii. p. 311 (1884) ; Dicks. Pl. Crypt. fase. i. 
p. 11; With. Arr. ed. 3, iv. p. 29. LL. saxicola Poll. Hist. Pl. 
Pal. p. 225 (1777); Engl. Bot. t. 1695. Placodium saaxicolum 
S. F. Gray Nat. Arr. i. p. 447 (1821). Squamaria sazicola 
Hook. in Sm. Engl. Fl. v. p. 197 (1833) ; Mudd Man. p. 129 ; 
Cromb. Lich. Brit. p. 44; Leight. Lich. Fl. p. 173 ; ed. 3, p. 158 
(incl, var. albomarginata) ; subsp. albomarginata Cromb. in Journ. 
Bot. xii. p. 147 (1874). 
Exsicc. Bohl. n. 55; Johns. n. 191; Larb. Lich. Hb. n. 213 
& Lich. Cantab. n. 24; Leight. n. 145; Mudd n. 92. 
A variable plant, which may form very large patches, with the 
centre often broken away; if sterile the lobes are crowded and 
imbricate, when fertile the centre of the thallus may be entirely 
