Nomurachlamys meisensis (Makiyama, 1926)
MAKIYAMA, J. 1926. Tertiary fossils from North Kankyô-dô, Korea. Memoirs of the College of Sience, Kyoto Imperial University [Serie B], 2 (3): 143-160, pls. 12, 13. [p. 156, pl. 13, fig. 4]
J. Makiyama, 1926, plate 13.
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«Holotype.— In Geol. Surv., Chôsen.
Shell about 70 mm. in height, higher than long, subequivalve and equilateral except for ears, rather thin, compressed, radially costate. Beaks small, sharply pointed, approximate. Ears very unequal, the anterior large, triangular, that of the right valve with a deep byssal notch; the posterior about two-thirds the length of the anterior, narrowly triangular, obliquely truncated behind. Discs right-angled above with the dorsal margins descending nearly straight toward the regularly rounded ventral margin, the anterior sice very slightly longer than the posterior. Left valve more inflated than the right which has a long ctenolium consisting of high sharp denticles. Sculpture: anterior ear of left valve with about 9 unequal, scaly radial riblets, that of the right valve divided into the upper area with 4 irregular round radial riblets, and the lower byssal area with flexuous, lamellated, horizontal, incremental lines; posterior ears with 4 to 6 low scabrous riblets, which interspaces with a feeble riblet; these riblets are obsolete near the upper margin; discs with 23 to 27 equal, equidisiant, flat-topped, roundly edged, dichotomous ribs; interspaces as wide as or a little wider than the ribs, usually with a scaly intercalating riblet. Development: prodissoconch small, oval, smooth; smooth ribs appear first, then the intercalating riblets; the ribs become dichotomous after reaching a height of about 30 mm.; in the adult, the ribs are scaly. Incremental lines very fine, not much imbricated. Interior obscurely radially grooved, ventral margin strongly crenate. Hinge with distinct cardinal crura; resilifer pit highly iriangular, deep, with rather sharply raised margins. Height, 68 mm.; length, about 65 mm.; diameter, 24 mm. (holotype). Height, 47 mm.; length, 44 mm.; thickness of the right valve, 8 mm. (paratype preserved in Geol. Inst. Kyôto Imp. Univ.) Occurrence.— Kinshôdô (Mankodô formation).» JIRÔ MAKIYAMA, 1926
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«Chlamys (Nomurachlamys) kaneharai closely resembles Chlamys (Nomurachlamys) meisensis (Makiyama, 1936) from the middle Miocene Mankodô Formation in the Meisen [= Meongcheon] area, North Korea. However, Ch. (N.) kaneharai is distinguished from Ch. (N.) meisensis by having a larger anterior auricle with a deeper byssal notch and a stronger byssal fasciole in the right valve. As pointed out by Kurihara (2010), Chlamys hataii Masuda and Akutsu, 1956 from the middle Miocene Nagaoka Formation in Tochigi Prefecture is a junior synonym of Ch. (N.) meisensis.»
MATSUBARA, T., I. NORO, Y. MATSUURA & T. IRIZUKI. 2014. Miocene Mollusca from the Ichibu Formation on Nishinoshima Island, Oki Islands, Southwest Japan. Paleontological Research, 18 (1): 6-32, figs. 1-11. [p. 18, 19]
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«Remarks: – This species differs from Chlamys kaneharai (Yokoyama) by its rather thick, subequivalved shell, larger number of radial ribs which are somewhat squarish, roundly flat-topped and divide into subequal two parts, and rather smaller anterior auricle than that of kaneharai. Chlamys arakawai (Nomura) is also related to the present one but differs by its higher shell, larger number of radial ribs which are rather low, inconspicuous intercalary threads and the characters of the hinge area.
Although this species has hitherto been reported from several localities of the Miocene formations of Japan without illustration, so far none of these records have been authenticated. Type locality, Geological formation and Age: – Kinseido, Eihoku-men, Kankyo-hokudo, North Korea. Heiroku formation. Early Miocene. Distribution: – Heiroku formation, Korea; Mizunami group, Gifu Prefecture (according to verbal communication of Itoigawa): both Early Miocene in age.» MASUDA, K. 1962. Tertiary Pectinidae of Japan. The Science Reports of the Tōhoku University [2nd. Series -Geology], 33 (2): 117-238, pls. 18-27. [p. 188]
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Chlamys meisensis (Makiyama); K. Masuda, 1962, Tertiary Pectinidae of Japan, plate 23, figure 2.
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