10 BKITISH IICHIWS : 



66. Urceolaria Ach. Thallns crustaceous, contirmous or areolate : 

 apothecia urceolato-impressed, with a proper and a thalline margin, 

 and spores septately murali-divided ; spermogones with somewhat 

 branched sterigmata and cylindrical spermatia. 



Snbtribe V. LECIDEEI Xyl. ThaUus variously cmstaceous, 

 pulverulent, or none proper ; gonidial layer consisting of gonidia 

 (rarely of chrysogonidia) : apothecia patellulate. 



67. Lecidea Ach. Thallus squamosa, areolate, pulverulent, or 

 none proper : apothecia biatorine, gyalectoid, or lecideine, with 

 simple or variously septate spores ; spermogones with simple or 

 simplish sterigmata and acicular, straight or arcuate, or shortly 

 cyliiidrical spermatia. 



68. Odontotrema Xyl. Thallus macular, indistinct : apothecia 

 thelotremoideo-lecideine or gj-mnotremoid, with simple or thinly 

 3-septate spores ; spermogones not observed. 



Tribe XIX. GRAPHIDEI Xyl. ThaUus crustaceous, thin, con- 

 tinuous, often but little visible, rarely wanting ; gonidial layer con- 

 sisting of gonidia : apothecia lirelline or rotundate. 



69. Xylographa Fr. ThaUus maculate, hypophlceodal : apothecia 

 lireUine or oblong, with simple spores ; spermogones with simple 

 sterigmata and acicular carved "spermatia. 



70. Agjrrinm Fr. ThaUus maculate, scarcely visible : apothecia 

 oblong or rotundate, with simple spores ; spermogones not known. 



71. Lithographa Xyl. ThaUus crustaceous or evanescent : apo- 

 thecia lirelline, with simple spores ; spermogones not yet seen. 



72. Opegrapha Humb. ThaUus usuaUy hypophlceodal or obsolete : 

 apothecia Uneari-lanceolate, subrotundate or Unear, with 1- or 

 multi-septate spores ; spermogones with simple sterigmata, and 

 cyUndrical, straight or arcuate spermatia. 



73. Platygrapha Xyl. ThaUus thin or obsolete : apothecia 

 plane, simple, with spurious thaUine margin and septate spores ; 

 spermogones with simple sterigmata, and cylindrical, straight or 

 slightly ciu'ved spermatia. 



74. Stigmatidium Mey. ThaUus distinct, crustaceous, thickish : 

 apothecia punctiform or elongate, with variously septate spores ; 

 spermogones with simple sterigmata and short, straight spermatia. 



75. Arthonia Ach. ThaUus thin, or hypophlceodal and eva- 

 nescent, rarely wanting, intemaUy sometimes with chrysogonidia ; 

 apothecia roundish or difform, plane or tumid, with variously 

 septate spores ; spermogones with simple sterigmata, and cyUndrical, 

 straight or curved spermatia. 



