An Inspection of the Oarai Flora of Upper Cretaceous Oarai Formation in Ibaraki Prefecture, Japan. : The fossil plants of Ibaraki.......no. I

摘要

Oarai plant bed was discovered by Ozaki and Saito in 1954 on the shore of the river Naka in the vicinity of Iwai, Oarai Town situated on the east of Mito City (text-fig. 1). In the cliff on the river bank it is intercalated in thick conglomerate beds (1300m. thick) which have been thought Cretaceous in age and nominated by them the Oarai Formation. There the last is conformably overlain by the Nakaminato formation, 1800m. in thickness. Last year, Zamiophyllum Sequoia and a fragment probably of Dicotyledonous plant were collected by them from this plant bed, and Late Cretaceous was suggested by the writer for the age of the plants. Ozaki and Saito, on the other hand, reported Cfr. Didymoceras ? sp. and Bostrychoceras sp. from the Nakaminato formation. Subsequently the writer collected from the Oarai formation 3 species in 3 genera of the Filicales, 1 species of the Equisetales, 5 species in 4 genera of the Cycydophyta, 2 species in 2 genera of the Coniferae, 18 species in 17 genera of