Abstract
As shown in the geological map in the Japanese text the Tetori series in the surveyed area is faulted and thiust at some places, and intruded by granitic rocks at others., Its base is unknown because of the igneous intrusion into the basal part., The series may be divisible into six formations in descending order as follows : f) Ogamigo upper Cyrena and Plant bearing formation e) Okurodani sandstone and conglomerate formation d) Otaniyama upper Perisphinctes bearing formation c) Mitarashi middle Cyrena and Plant bearing formation b) Nonomata lower Perisphinctes bearing formation a) Ushimaru lower Cyrena and Plant bearing formation The occurrences of Perisphinctids and other marine shells in the two formations are discoveries made by the present research., These marine formations alternate with the non-marine ones and the latter yield plant fossils., Formarly OISHI claimed that the plant beds indicate one definite horizon in the Tetori series, but in fact they are distributed in various horizons from top to base as KOBAYASHI has already pointed out., As the opinion that the Jurassic period was a time of tranquility insofar as volcanism is concerned has been current among the Japanese geologists, the find of acidic tufflayers in the Ushimaru and Mitarashi formations are facts hitherto unknown.,
