During the collecting season of 1948, from late June to October, the University of Michigan maintained a botanical expedition in Mt. Rainier National Park, Washington. Dr. A. H. Smith who conducted the survey was assisted by Henry A. Imshaug and Emory G. Simmons. Dr. D. E. Stuntz of the Department of Botany, University of Washington, joined the group in July. They obtained abundant collections of Otidea species which, with the collections in the University of Michigan Herbariumi, form the basis of this investigation. The writer recognizes ten species and three varieties. This number materially exceeds the number in previous published reports for North America. Seaver (1928) reported three under the name Scodellina. One new species, 0. rainierensis, and one new variety, 0. alutacea var. microspora, are described from the Mt. Rainier collections and one new species, O. Kauffmanii, is named from Michigan material. The types of new species described here are deposited in the University Herbarium of the University of Michigan. The genus Otidea was established by Fuckel (1869-1870) for Pezixa leporina Pers. ex Fr., P. onotica Fr., P. cochleata L. and P. abietina Pers. The principal diagnostic character by which species of Otidea differ from those in Pesiza is the presence of a split in the apothecium. Fuckel (I.c.) in his diagnosis of the genus described the paraphyses as subclavate although he included 0. leporina and 0. onotica in which the paraphyses are hooked and not subclavate. Since the genus was established, several species which have filiform or filiform-subclavate paraphyses have been described for it. Boudier (1885) considered the straight paraphyses as distinctive and established the genus Wynnella based in part on such paraphyses. 0. auricula Schaeff. was