Patinopecten kagamianus nimaensis Masuda, 1958
MASUDA, K. 1958. On the Miocene Pectinidae from the Environs of Sendai; part 12, On Pecten kagamianus Yokoyama. Transactions and Proceedings of the Palaeontological Society of Japan [N. S.], 32: 271-284, pls. 40, 41. [p. 277, pl. 41, figs. 1, 2]
Patinopecten kagamianus nimaensis
MASUDA, n. subsp. Plate 41, figures 1, 2. «Shell moderate, moderately thick, higher than long, compressed, equilateral except for auricles; right valve nearly equal or a little more convex than the left; both valves radiately ribbed and forming an angle of about 90º at apex.
Right valve with about 11, elevated, round-topped, smooth radial ribs, and fine concentric growth lines, ornamented by obtuse network; radial ribs much broader than their interspaces on upper half of disc but tend to become subequal towards the ventral margin, and divided into several, fine riblets by shallow longitudinal furrows, and rarely dichotomous near the beak with narrow intcrspaccs; riblets on the backs of radial ribs on central part of disc usually appear near the ventral margin, but at the lateral portions they appear on upper half of disc; radial ribs at the lateral portions of disc very low and weak; interspaces between the radial ribs rather smooth, but sometimes with a single or a few, faint intercalary threads; anterior auricle nearly equal to the posterior one, sculptured with several radial threads and concentric lines, and furnished with wide and shallow byssal notch and rat her wide byssal area; posterior one similar to anterior in sculpture. Left valve with elevated radial ribs and weak concentric growth lines, and ornamented by fine network; radial ribs narrower than their interspaces, rather sharp near the beak, tend to become rounded and broad towards the ventral margin, and divided into a few, fine riblets by shallow longitudinal furrows on lower half of disc; radial threads on the backs of radial ribs fine and weak. but the middle one extends to the beak; radial ribs at the lateral portions low and slender; auricles sculptured with several, fine radial threads and concentric lines; hinge with simple cardinal crura, and wide and shallow resilial pit provided with shallow lateral sockets. Interior surface gently folded. Dimensions:— Shown in Table 1. Comparison and Affinity:— This new subspecies can be distinguished from kagamianus moniwaensis by the shell being higher than long, small apical angle, elevated radial ribs, rather wide and deep interspaces, and fine network in the right valve. Also it can be distinguished from kagamianus kagamianus by the higher shell, less number of radial ribs, and smaller apical angle. Remarks:— This new subspecies is characterized by its higher than long, compressed shell, fine network on the surface, 11 to 12, round-topped radial ribs which are a little broader than or nearly equal to the interspaces in breadth, and divided into several, fine riblets by shallow longiitudinal furrows near the ventral margin on the central part of disc and on upper half of disc at the lateral extremities, and by the left valve having rather distinct network on the surface, elevated radial ribs which are divided into a few, fine riblets by shallow longitudinal furrows. Type locality, Geological formation and Age:— Railroad cutting on the San-in Line at Akazaki, Nima-machi, Nima-gun, Shimane Prefecture. Lat.: 35º00'43" N ., Long. 132º24'40'' E. Kawai formation. Early l\liocene. Depository:— Holotype, Reg. No. T.NM. 26,Geological and Mineralogical lnstilute, Faculty of Science, Hiroshima University. Paratype, DGS, Reg. No. 3580. Occurrence:— Kawai formation at type locality and Tachime, Nima-machi. Nima-gun, and Tamatsukuri formation at Ushirobane, Mitoya·machi, Hanseki-gun, all in Shimane Prefecture.» KÔICHIRÔ MASUDA, 1958
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K. Masuda, 1958, plate 41.
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