PLACODIUM | PHYSIACEA 217 
times imperfectly lobed or crenate at the circumference, bluish- 
grey or greyish-white (K—). Apothecia plane, round or 
irregular in form, orange- or tawny-red (K + deep purple), the 
thalline margin thickish, sometimes flexuose; spores broadly 
ellipsoid, 12-16 » long, 8-9 » thick.—Lichen arenarius Pers. in 
Ust. Ann. Bot. vii. p. 27 (1794) (non Retz.) ; Dicks. Pl. Crypt. 
fase. iv. p. 23, t. 12, fig. 2. L. exsiorufus Sm. Engl. Bot. n. 1040 
(1802) (non Schrad.). Patellaria erythrocarpa Pers. in Ann. 
Wett. Ges. ii. p. 12 (1810). Lecidea erythrocarpia Ach. Lich. 
Univ. p. 205 (1810). Lecanora teicholyta Ach. tom. cit. p. 425: 
Cromb. in Grevillea xviii. p. 45 (1889) & Monogr. i. p. 365. 
L. rubricosa Ach. Syn. p. 162 (1814) pro parte. Lecanora 
arenaria Cromb. Lich. Brit. p. 46 (1870) ; Leight. Lich. Fl. p. 233 ; 
ed. 3, p. 212. Rinodina rubricosa 8. ¥. Gray Nat. Arr. i. p. 452 
(1821). Callopisma arenarium Mudd Man. p. 138 (1861). 
Exsicc. Larb. Lich. Hb. n. 96. 
Distinguished by the thick furfuraceous thallus and by the 
habitat. Often confused with Pl. cxsio-rufum, but differs, among 
other characters, in the absence of thalline reaction with potash. 
Hab. On sandstone rocks and walls, rarely on bricks in maritime 
and inland districts.— Distr. Rather rare in the Channel Islands, S.E. 
and W. England and in S. Wales.—B. M. Jersey; I. of Wight; 
Shoreham, Fairlight near Hastings, Pulborough and Midhurst, 
Sussex; near Hereford; near Monmouth; near Lyndstep, Pembroke- 
shire; Bury St. Edmund’s, Suffolk; Strumpshaw, Norfolk; Wisbech 
and Waterbeach, Cambridgeshire. 
Thallus whitish ; reaction with potash various. 
26. Pl. Lallavei Oliv. Lich. Eur. p. 99 (1909).—Thallus 
determinate, thickish, smooth, tartareous, cracked-areolate, 
chalky-white (K — ). Apothecia subinnate, with a thin thalline 
margin, becoming immarginate, bright-rusty or blood-red (K + 
dark crimson) ; spores ellipsoid-oblong, 8-12 p long, 4—7 p thick. 
—Lecidea Lallavei Clem. Ensayo, p. 295 (1807).  Lecanora 
Lallavei Nyl. in Mém. Soc. Sci. Nat. Cherb. v. p. 112 (1857) ; 
Cromb. Lich. Brit. p. 46 & Monogr. i. p. 366; Leight. Lich. Fl. 
p. 223; ed. 3, p. 212 pro parte. 
Allied to the preceding species, but differs in the structure of the 
thallus, innate apothecia and smaller spores. 
Hab. On caleareous rocks and walls in maritime districts.— Distr. 
Rare in S.W. and S. England and S.E. Ireland.—B. M. I. of Wight ; 
Lower Glanmire Road, Cork. 
27. Pl. albolutescens A. L. Sm.—Thallus thin and furtur- 
aceous, or thickish and areolate, whitish, or evanescent (K — ). 
Apothecia moderate in size or small, dark-orange, with a paler 
prominent persistent proper margin (IX + crimson) ; paraphyses 
branched and thickly septate towards the tips; spores broadly 
