Parvamussium habunokawense (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. 344, pl. 1, figs. 14, 15]
1951 Propeamussium habunokawensis Kimura, 1951
T. Kimura, 1951, plate 1.
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«Propeamussium habunokawensis KIMURA, n. sp.
PI. I, Figs. 14, 15. Description:— Shell small, inequivalve, subequilateral, slightly higher than long.
Right valve fairly convex, nearly orbicular, antero- and postero-dorsal margin nearly straight, the former being a little longer than the posterior, its antero-ventral margin rounded and sinuated below; posterior ear truncated behind obliquely; hinge line straight, as long as about two-thirds the whole length. Surface covered by numerous fine concentric lines which are especially distinct near the periphery of the ears. Internally, nine internal ribs impressed almost in their whole length from umbo to venter, but do not reach the ventral extremity. ln the left valve the anterior ear a little longer than the posterior, but their outlines are similar to each other. Surface ornamented by a fine lattice-work made by numerous irregular radial striae, radial lines and crowded concentric lines. About nine radial internal ribs narrower and shorter than those of the right valve. Comparison:— This species is distinguished from Pecten (Propeamusium) cowperi var. yubarensis YABE and NAGAO (1928, p. 88, pI. 16, fig. 17-19) in having unequal ears and more internal ribs than the latter. It is somewhat similar to Variamussium laeviradiatum (WAAGEN) by PARIS and RICHARDSON (1915, p. 538, pI. 44, fig. 1), but the latter has dorsally prolonged ears and more regularly disposed ribs on the left valve.
Occurrence:— Habunokawa, north of Torinosuyama and Nioigataki.» TOSHIO KIMURA, 1951
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