10 BBITISH LICHEtfS : 



66. Urceolaria Ach. Thallus crustaceous, continuous 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. 



Subtribe V. LECIDEEI Nyl. ThaUus variously crustaceous, 

 pulverulent, or none proper ; gonidial layer consisting of gonidia 

 (rarely of chrysogonidia) : apothecia pateUulate. 



67. Lecidea Ach. Thallus squamose, 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 

 cylindrical spermatia. 



68. Odontotrema Nyl. Thallus macular, indistinct : apothecia 

 thelotremoideo-lecideine or gymnotremoid, with simple or thinly 

 3-septate spores ; spermogones not observed. 



Tribe XIX. GBAPHIDEI Nyl. Thallus crustaceous, thin, con- 

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

 sisting of gonidia : apothecia lirelline or rotundate. 



69. Xylographa Fr. Thallus maculate, hypophloeodal : apothecia 

 lirelline or oblong, with simple spores ; spermogones with simple 

 sterigmata and acicular carved spermatia. 



70. Agyrinm Fr. Thallus maculate, scarcely visible : apothecia 

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



71. Lithographa Nyl. Thallus crustaceous or evanescent : apo- 

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



72. Opegrapha Humb. Thallus usually hypophloeodal or obsolete : 

 apothecia lineari-lanceolate, subrotundabe or linear, with 1- or 

 multi-septate spores ; spermogones with simple sterigmata, and 

 cylindrical, straight or arcuate spermatia. 



73. Platygrapha Nyl. ThaUus thin or obsolete: apothecia 

 plane, simple, with spurious thalline margin and septate spores : 

 spermogones with simple sterigmata, and cylindrical, straight or 

 slightly curved spermatia. 



74. Stigmatidium Mey. Thallus 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, internaUy sometimes with chrysogonidia : 

 apothecia roundish or difform, plane or tumid, with variously 

 septate spores ; spermogones with simple sterigmata, and cylindrical, 

 straight or curved spermatia. 



