Solitary specimen which occurs. Apothecia crowded, in the specimen; of almost middling size; sessile; a rather thick, at length flexuous margin, which is white below, but black- en above, bordering, not prominent, so flat, naked, brownish-black disk; which is encircled by a thick, colourless hypothecium, resting on the gonidial layer. Spores always colourless (the sporoblast in their most perfect state, shewing only a slight yellowish tinge, often imperceptible) from short- ellipsoid becoming rather oblong-ellipsoid, with obtuse tips; deplcate-dy- blastish; the two regular sporoblasts (which in one stage of development occupy only the middle of the spore, and meet, or are connected by an isthmus) filling at length the ends of the spore, and the rather wide intervening space cropped by this, often obscure, then di-segment; from twice to twice and a half longer than wide. Paraphyses articu- late, often conspicuously. The lichen has the aspect of Lecidea, but the spores, if I do not mistake, indicate its affinity with Lecanora, in several groups of which, Lecideine forms commonly occur. There is not in fact wanting some resemblance in our plant to Lecanora Bischoffii (Hepp sub Psora, Lich. Eur. n. 81. Rabenhorst Lich. Eur. n. 77. Ainoimia, Koerb. Parerg. p. 75) both as respect apothecia and spores; but the former are much smaller in the European lichen, and the latter coloured. L. oreina, Ach. Syn. p. 181. Nyl. Lich. Scand. p. 142. Parmelia, Fr. Lichenogr. p. 113. Schær. Spicil. p. 416; & Lich. Helv. n. 331. Tuckerm. Synops. p. 37. Cretaceous sandstone, Deer Creek, North Platte; and at the base of the Big Horn Mountains, Hayden. L. Sophodes, Ach. Lichenogr. p. 356; Syn. p. 153. Parmelia, Ach. Meth. p. 155. Fr. Lichenogr. p. 149, excl. β. Tuckerm. Synops. p. 41. On dead branches of Sarcobatus, Deer Creek, North Platte; Hayden Spores about eight in a spore-sack. L. cinerea (L., Fr.) Nyl. Prodr. Gall. p. 81; Lich. Scand. p. 153, pr. p. Parmelia, Fr. Lichenogr. p. 142. Rocks. Red Buttes, and at Deer Creek, North Platte; also at the base of the Big Horn Mountains. Hayden. The specimen all more or less app- roaching that has been separated as var. protuberans, Fr. l.c. (L. cinerea, v. gibbosa, Nyl. l.c. Ureolaria gibbosa, Ach.)