Radulopecten nagatakensis (Kurata & Kimura in Kimura, 1951)
KIMURA, T. 1951. Some pectinids and a limid from the Jurassic Torinosu group in Japan. Journal of the Faculty of Science, University of Tokyo [Section II: Geology, Mineralogy, Geography, Seismology], 7 (6-10): 337-350, pI. 1 [p. 338, pl. 1, fig. 1]
1951 Chlamys nagatakensis Kurata & Kimura in Kimura, 1951
T. Kimura, 1951, plate 1.
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«Description:— This species is based on an external and an internal mould of a right valve.
Shell nearly fiat, ovate, higher than long, equilateral; anterodorsal margin slightly concave, postero-dorsal nearly straight. Surface provided with 7 principal radial ribs, median one being the widest (about 4.5 mm on the ventral margin); these ribs broad and round on the ventral side, but very narrow and somewhat angular near the umbo; on the principal ribs there are 4 to 5 narrow, but sharp riblets which are separated from one another by fairly wide furrows; fine radial lines seen on the ribs and their interspaces; the interspace as broad as or slightly narrower than the rib. Besides these radial ornaments there are concentric striae, more or less regularly disposed; between the striae there are dense delicate concentric lines which are a little projected above at their junction with radial riblets; delicate lattice-work made by concentric lines and radial lines especially distinct on the ventral side of the interspaces. Hinge line straight; anterior ear fiat, about one tpird as long as the whole length of the shell, and its ventral margin distinctly sinuated; posterior ear not well preserved. Dimension:— Holotype (No. 7090) is 27 mm in length and 34.1 mm in height and its umbonal angle 72 degrees. Comparison:— The relatively high outline, acute umbonal angle and the mode of ornamentation are the characteristics of this species. Eopecten doultingensis PARIS and RICHARDSON (1915, p. 531. pI. 46, fig. 1) looks similar to this in the ornamentation, but broader and has ten principals. Occurrence:— Nagatake.» NOBUO KURATA & TOSHIO KIMURA, 1951
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