710. SOME NEW BIVALVE SPECIES FROM THE LOWER GYEONGSANG GROUP, KOREA

Abstract

Two new bivalvian species from the Yeonhwadong Formation, the lowermost formation of the Gyeongsang Group are described here. Trigonioides (Koreanaia) bongkyuni sp. nov. is ornamented with large angled V-shape subradial ribs of Koreanaia type and possesses fine crenulated hinge teeth of Wakinoa type. On account of the stratigraphic relation as well as the morphologic characters, T. (K.) bongkyuni is reasonably interpreted as a link-species between T. (K.) cheongi and some species of T. (Wakinoa) in the evolutionary lineage. The other new one, Pseudohyria matsumotoi, may be considered to be an ancestor of other species of Pseudohyria reported from the continental side of Asia in respect of the stratigraphic occurrences.