樺太散江郡野頃産マンモスElephas primigenius (BLUM.,)齒化石に就いて

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§ In this paper is treated a right lower third molar (M^-_3) of the so-called Mammoth Elephas primigenius (BLUMENBACH)., The state of preservation of the present specimen, though slightly waterworn, is rather good, and deeply worned by grinding nearly to the root of the ridges at the posterior part., § In the crown view, the outer side of the tooth is nearly straight and the other slightly convex., The gringing surface is oval and represents rather deep concavity., The length of the crown is 206 mm., while that of the grinding surface is 202mm., The maximum width of the crown (also that of the grinding surface) is 73mm., at the eleventh ridge., The greatest height of the crown is 192mm., at the hindermost ridge and that of the crest is about 60mm., at the fourteenth ridge., It consists of sixteen ridges excluding the anterior and posterior talons., The frequency of ridges in the length of 100mm., is about 10 in the grinding surface., All the ridges are distinctly exposed, with light brown coloured dentines, creamy white coloured enamels and chocolate brown cements., The ridges are weakly flexuous, the anterior and the posterior side of them being nearly parallel; they are almost straight in the anterior part of the crown, while it is convex anteriorly in the posterior part., The interspaces between the ridges are each nearly 5mm., in width and the breadth of the ridge itself is about 7-8mm., The enamel layer of the ridge is rather thin, about 1.,2mm., thick in the external and internal marginal parts of the ridge, showing no constrictions and having slight coarse plications., § The present specimen is said to have been found by a fisherman on the beach in th Nokoro village on the coast of Taraika Bay of Japanese Saghalin., Therefore, its geological mode of occurrence is regretably uncertain, but considering all the circumstances, it was derived most probably from the raised coastal plain deposits, the Rukutama Series of upper Diluvial age., This series, ten meters in thickness with the overlying so-called "Tundra" bed and the underlying upper Pliocene Nokoro bed, togerher builts up the sea cliffs of about twenty ot fifty meters high and is composed of loose sand, mud and gravel, intercalating thin layers of clay and peat., § The occurrence of the present molar is remarkable from palaeogeographical point of view, as no remains of a Mammoth were hitherto known from the northern Japanese Islands; shortly, it suggests us the presence of a state of land connection between Saghalin Island and the Asiatic continent at some date of the Diluvium, as the occurrence of the Mammoth fossil is well known from the Siberian and Manchurian Diluvial deposits.,
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樺太散江郡野頃産マンモスElephas primigenius (BLUM.,)齒化石に就いて

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