Patinopecten kimurai nakosoensis Masuda, 1960
MASUDA, K. 1960. On the Miocene Pectinidae from the Environs of Sendai; Part 16, Pecten kimurai Yokoyama and Palliolum cf. peckhami (Gabb). Transactions and Proceedings of the Palaeontological Society of Japan [N. S.], 38: 249-262, pIs. 29-30. [p. 256, pl. 29, figs. 2, 3]
«Patinopecten kimurai nakosoensis
MASUDA, n. subsp. Plate 9, Figures 2, 3 Descripton:— Shell moderate, rather thin, suborbicular, compressed, equilateral except for auricles; right valve somewhat more convex than left; radiately ribbed and forming an angle of about 100º at apex. Right valve gently inflated, with about 9, elevated, round-topped radial ribs, fine concentric growth lines and obtuse network; radial ribs broader than their intcrspaces, divided into two or three, faint, fine radial threads by shallow longitudinal furrows near beak but tend to become obsolete downwards, and usually provided with several, faint, fine longitudinal striae or riblets on their hacks and flanks; radial ribs near submargins low and slender, much narrower than their interspaces and sometime dichotomous; longitudinal striae usually appear at lower half of disc, and rather more distinct near submargins than on central part of disc, but not seen in young shell; interspaces between radial ribs gently rounded and smooth-bottomed, but sometimes provided with a few, very faint, fine longitudinal striae near submargins; anterior auricle furnished with wide and shallow byssal notch, rather wide byssal area, with several, faint, fine radial threads, concentric lines, and posterior one similar to anterior in sculpture; hinge with distinct cardinal crura, wide and shallow resilial pit with wide-opening. rather low lateral ridges, and ill-developed ctenolium in young shell. Left valve gently inflated, with distinct, rather elevated radial ribs, fine concentric growth lines and rather distinct, fine network; radial ribs rather sharp near beak, usually tend to become rather rounded, and with a few, fine longitudinal riblets, or rarely they divided into to or three, rather distinct, line radial threads by shallow longitudinal furrows on upper half of disc; radial ribs near submargins low and slender, and sometimes their interspaces with a few, faint, fine longitudinal striae; interspaces between radial ribs gently rounded and smooth-bottomed, rarely with intercalary threads which usually appear near beak; anterior auricle somewhat larger than posterior, with several, fine radial threads and concentric lines, and posterior one similar to anterior in sculpture. Interior surface of valves gently folded corresponding to external sculpture.
Dimensions:— Table I. Comparison and Affinity:— This new subspecies differs from kimurai by the right valve having rather more elevated radial ribs and by the left valve with radial ribs which are less elevated and sharp, and usually with a few, fine longitudinal riblets on their backs and by the subequivalved shell. Also it is distinguishable from murayamai by its rather thin shell, rather less elevated radial ribs of the right valve and by the left valve having rather well developed longitudinal striae or riblets.
Type locality, Geological formation and Age:— Road-side cliff at Kokozura. Nakoso City, Fukushima Prefecture (Lat. 36º51'18'' N ., long. 140º47'37'' E.). Kokozura formation. Middle Miocene. Depository:— Holotype. DGS. Reg. No. 1930, Paratype, DGS. Reg. No. 3713. Occurrence:— Kokozura formation at the type locality. upper part of Kadonosawa formation and Suenomatsuyama formation in lwate Prefecture and Takahoko formation in Aomori Prefecture: — all Middle to Late Miocene in age.» KÔICHIRÔ MASUDA, 1960
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K. Masuda, 1960, plate 29.
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