172 PROCEEDINGS OP THE AMERICAN ACADEBIY 



Placodium atroalbum ; tliallo tenui granuloso dein 'et rimoso- 

 areolato luteolo-fuscescente ; apotheciis (latit. c. 0,3-0,5 mm.) adnatis 

 zeorinis, margiiie thalliuo tenui demisso integro albo discum margina- 

 tum nigi-um nudum cingente, intus incoloribus. Sporoe octonte, ellip- 

 soidea3, polari-biloculares sporobl. approximatis, lougit. 0,014-23"""-, 

 crassit. 0,005-9"""-, paraphysibus filiformibus fusco-capitulatis demum dis- 

 tinctis articulatisque. — On cretaceous sandstone and chalcedony, North 

 Platte, Rocky Mountains, Dr. Hayden. Lime rocks, Utah, Mr. Lapham. 

 Of the stock of P. variahile (Pers.) Nyl., which occurs with well- 

 marked distinctness from this in the same region ; and closely asso- 

 ciable with the P. Agardhianum of Anz. Lich. Langob. n. 37. But 

 our lichen is scarcely as well comparable with the P. Agardhianum of 

 Hepp {Lich. exs. n. 407), and differs still more from the specimen 

 before me of Pyrenodesmia Agardhiana, Mass. (Arn. in herb. Koerb.)^ 

 which is wholly lecideoid. This last is represented here by a lichen of 

 the Alabama lime rocks {Judge Peters). If all these be to be taken 

 for states of the same variable species, our Rocky Mountain lichen 

 above described is, with little doubt, another. The polar type is not 

 easily made out in the spores of the latter ; which, but for the other 

 structure of the hymenium, might be supposed rather a Lecanora akin 

 to L. erysibe (Ach.), Nyl. There are no reactions of the thallus with 

 potash or chloride of lime. 



Lkcanora. Semitensis, sub-sp. nov. : thallo e squamulis glebosis 

 stramiueis mox crenato-lobatis subinde hypothallo nigro marginatis ; 

 apotheciis (0""" , 7-1"""- latis) appressis plano-convexis tumentibusque 

 congestis, disco livido-fuscescente albido-pruinoso, margine demum sub- 

 granulato vel excluso. Hypothecium incolor. Sporoe octonoe ellip- 

 soide£E simplices incolores, longit. 0,011-10"""-, crassit. 0.005-6"™-.— 

 Granitic rocks, Yosemite Valley, California, Dr. Bolander. Clearly 

 a member of the Saxicola group, and very close to L. saxicola v. dif- 

 fracta, from which (largely exhibited on the Californian rocks) the 

 present differs in its scaly thallus, which is not radiant, and the ultimate 

 development of its fruit. 



Lecanora glaucovirens, sp. nov. : thallo crustaceo orbicular! 

 verruculoso-granulato viridi-glaucescente versus ambitum albido, hypo- 

 thallo incolore; apotheciis (latit. 0'""'-, 7-1"""-) appressis, disco mox 

 convexo e livido-fusco nigrescente, margine integerrimo. Hypothecium 

 pallidum. Sporaj octonaj, ellipsoideoe, simplices, incolores, longit. 

 0,014-17'""-, crassit. 0,006-9, paraphysibus conglutinatis. Spermatia 

 acicularia arcuata. 



On bark, Galapagos Islands, South America, Rev. T. Hill (Hassler 



