200 ON LICHENS COLLECTED TN ARCTIC AMERICA. 



Arthonia, Ach, Nyh 



No. 158. A. TUMIDULA, Leighton. Thallus pallide cinerascens, opacus, 

 tenuis ; apothecia parva nigra, sessilia, subastroideo-difformia, con- 

 vexa, papillosa; sporae 8, magnse, oblongse, medio constrictre, murall- 

 divisae (septis horizontalibus 7-8) fuscae ; gelatina hymenea iodo ftil- 

 vescens. Ad cortieem laevem Alni. 

 Hab. River St. Mary's, Lake Superior. 



PLATE IT. 



Fig. 6. Aseus, magn. 330 lin. Fig. 7. Spores, magn. 1200 lin. 



Odontotrema, Nyl. 



No. 159. O. Richardsonii, Leighton. Thallus macula albido-cinera- 

 scente dilatata indicatus ; apothecia mediocria fusco-nigra, rotundata, 

 adnata, patellariodea, pars excipuli superior dentibus multis versus 

 centrum concavum concolor apertum radiatim vel couniventer versis; 

 sporse 4, incolores, aciculares vel vermiformes, arcuatse, uniseptatse; 

 pnraphyses graciles confertse; gelatina hymenea iodo cserulescens, 

 deinde vinose tincta. 

 Hab, On weathered wood. Fort Enterprise. 



PLATE II. 



Fig. 1. Spores, magn. 1200 lin. 



t 



