Taxonomical and Paleoenvironmental Study of Genus MELONIS (Benthec Foraminifera)

根据在四国近海、大东海岭附近、小笠原群岛以东和沙茨基海隆附近采集的4个活塞柱标本，对作为第四纪至近代深海底水指示的钙质底栖有孔虫属Melonis进行了分类学和古生态学研究，并对该属的分类和种内变异进行了生物统计学分析。几种参考材料用于分类比较。它们是赤道太平洋、鄂霍次克海和地中海等参考海区的少量沉积物。affinis，M. A和M. barleeanus被确定在晚更新世至全新世序列的活塞核心。该属的膨胀型与典型的M.地中海地区的pompilioides。Melonissphaeroides包含冷水品种，这是在两个较浅的网站发现。Melonis affinis的特点是非常细的穿孔壁，只在两个较深的网站被发现Melonis barleeannus在边缘壁的程度上有更广泛的变化，形式（典型的M. barleeanus多具缘1个M.尼科巴森病形式）。后一种形式已被确定为M。parkerae，并采集了大量的标本，对化石种的分布进行了研究。目前，在从北海道到冲绳的始新世晚期到更新世晚期发现了甜瓜属植物的标本。这些分类学研究是连续进行的。

The genus Melonis, which is a calcareous benthic foraminiferal genus and regarded as an indication of deep-sea bottom water in the Quaternary to Recent, is exmained taxonomically and paleoecologically.The taxonomy and intraspecific variations of the genus in the Northwest Pacifec are biometrically examined based on the specimens from four piston-cores collected from off Shikoku, near the Daito Ridge, east of Ogasawara Islands and near the Shatsky Rise. Several reference materials are used for the taxonomic comparison. They are a few rescent sediments from the equatorial Pacific Ocean and Okhotsk Sea and some reference areas including the Mediterranean region.As a result, Melonis sphaeroides, M. affinis, M. SP. A and M. barleeanus are identified in the late Pleistocene to Holocene sequences of the Piston-cores. The inflated form of the genus is distinguished from the typical M. pompilioides in the Mediterranean region. Melonissphaeroides contains a cold -water variety, which is found in the two shallower sites. This variety is living in the Okhotsk Sea.Melonis affinis, characterized by very finely perforated wall, is found only in the two deeper sites Melonis barleeannus has wider variation on the degree of limbate wall, form (typical M. barleeanus to much limbate one M. nicobarensis-form). The latter form has been identified as M. parkerae by some authors.A lot of samples have been collected to recognize distribution of fossil species. In this moment, specimens of Melonis have been found in the upper Eocene to lower Pleistocene from Hokkaido to Okinawa. Those taxonomic study is performed continuously.