explorations in Nebraska, and the Indian Territory. The plant is otherwise only known in Southern Europe, and Northern Africa. It is nearest to L. canescens, which has a rather more crustaceous habit, and a wider geographical range; occurring also not uncommonly on trees; but the latter is unknown here. L. parasema (Ach.) Nyl. Prodr. Gall. p. 123; Lich. Scand. p. 216. Lichen, Ach. Prodr. p. 64, pr. p. Lecidea, Ach. Met. p. 35, pr. p. var. enteroleuca, Nyl. l. c.; & Lich. Par. n. 57, Lecidea enteroleuca, Ach. Lichenogr. p. 177; Syn. p. 19. Fr. Lichenogr. p. 331; & Lich. Succ. n. 27. Tuckerm. Synopsis. p. 67. On rocks (creaceous sandstone) Deer Creek, North Platte, Hayden. Thallus whitish; areolate ; the hypothallus obscure. Apothecia smallish; soon convex and inimarginate; the naked disk exposed upon a colourless hypothecium. Spores in eight; ovoid-ellipsoid; simple; bimalbate; once and a half to twice longer than wide. L. vitellinaria, Nyl. Bot. Notis in Bot. Notis. 1852; Lich. Scand. p. 218. Th. Fr. Lich. Arct. p. 222. Parasitic on the crust of Lecanora vitellina, growing upon rocks. Creaceous sandstones, Deer Creek, North Platte, Hayden. Apothecia minute; scattered here and there on the (sterile) crust of the cited Lecanora; the disk commonly exceeded by the margin. Spores colourless; short-ellipsoid; simple; becoming once and a half longer than wide. I have not yet observed these little apothecia on any other specimens than those collected by Dr. Hayden. L. geminata, Flot. in Zw. exs. fide Nyl. Prodr. p. 129; Lich. Scand. p. 234. Rhizocarpon, Koerb. Syst. p. 259. / L. atroalba, Fr. Lichenogr. p. 310, pr. p.; & Lich. Succ. n. 406, A. / L. dispora, Naeg. in Hepp Lich. Eur. n. 28. Rhiz L. Montagnei, Flot. msc. / Rhizocarpon, Koerb. l. c. Rabenh. Lich. Eur. n. 329. L. confervoides, v. atroalba, Schær. Spicil. p. 128; & Lich. Helv. n. 443. Granitic and other rocks. On creaceous sandstone, Red Buttes, North Platte; and at the base of the