Rev. W. A. Leighton on the British Graphideae. 389 



" Arthonia marginata, Dufour, Joum. Phys. 8/. 205." (1818) (fide Fries 



et Schaerer). 

 Platygramme Lyellii, Mever in Spreng. Sj'st. Veg. 4. p. 1 . 255 (excl. E. Bot. 



1813) (1827). 



New Forest, Hampshire ! Mr. Lyell in herb. Borrer. 



ThaUus thin, membranous, of a dull dirty yellow or olive colour, 

 smooth and waxy in appearance, veiy similar to some states of 

 Verrucaria nitida, Schrad., limited by a dark brown wavy irre- 

 gular line. LirellcE numerous, scattered irregularly, more or 

 less crowded, prominent and sessile, oblong or linear-oblong, 

 rounded aud obtuse at each extremity, for the most part simple, 

 straightish, the margin variously waved and curved, occasionally 

 branched, though apparently in general the result of confluence ; 

 — there are also smaller lirellae of an irregular rounded form in- 

 terspersed. Disk broad, flat or concave, of a dull dark brown, 

 more or less pruinose, surrounded by a narrow prominent ele- 

 vated wavy black proper margin, and encompassed by an elevated 

 rounded spurious thallodal margin, very conspicuous by its white 

 colour and pulverulent appearance. A vertical section shows 

 the perithecium to subtend the base of the disk, just as in an 

 Opegrapha, not at all resembling the fig. 2 of the genus Leior- 

 reuma in Eschweiler's Syst. Lich. 13, though the author remarks, 

 "anatomiam optime reprseseutat 111. Sowerbyus icone Opegrap ha 

 Lyellii ejus (Eug. Bot. vol. 27. tab. 1876)," where the structure 

 is identical with our Plate V'lL fig. 24 a. 



The structure of the lirella distinguishes it from Graphis 

 Sinithii {Opeg. scripta, E. Bot.), aud that together with the 

 sessile lirellge with their white thallodal margin aud its general 

 habit from Hynienodecton dendriticurn. 



Plate Vll. fig. 24. a, Vertical section of thallus and lirella; b. sporidia. 



5. Aulacographa. 



Apothecium lirellseform, subimmersed, prominent; perithe- 

 cium carbonaceous, dimidiate or confined to the sides, palmatifid, 

 the base naked ; disk rimseform, closed, surrounded with a proper 

 longitudinally furrowed margin and an accessory thallodal margin. 

 Thallus membranaceous. 



Name from avka^, a furrow, and ypacjitj, writing, in allusion 

 to the furrowed proper margins. 



1. Aulacographa elegans. Thallus membranaceous, subtarta- 

 reous, orbicular, granulated or rugose, determinate; lirellae 

 erumpent, prominent, sessile, oblong or lineari-elongate, simple, 

 straight or curved ; proper margin thick, tumid, prominent, lon- 

 gitudinally furrowed ; thallodal margin thin, membranous ; disk 

 rimaiform ; spol-idia in asci, lineari-elongate, with a broad mem- 



