Mizuhopecten paraplebejus (Nomura & Hatai, 1936)
NOMURA, S. & K. HATAI. 1936. Fossils from the Tanagura Beds in the Vicinity of the Town Tanagura, Hukusima-ken, Northeast Honsyû, Japan. Saito Ho-on Kai Museum Research Bulletin, 10: 109-155, pls. 13-17. [p. 119, pl. 13, figs. 1, 2; pl. 16, figs. 6, 7]
1936 Pecten (Patinopecten) paraplebejus Nomura & Hatai, 1936
S. Nomura & K. Hatai, 1936,
plates 13, 16. |
«Shell resembling P. yessoensis JAY in general respects, rather large, thin, orbicular, inequivalve. Right valve moderately convex, equilateral except for ears, ornamented with about twenty, very low, broad, flatly rounded, smooth, radial ribs, rarely with a faint medial sulcus, and tend to become obsolete on lower half of disc-surface; interspaces between ribs very shallow and narrow, about one-third of ribs in breadth in middle part of disc; surface also marked by rather coarse, somewhat irregular lines of growth; hinge-line a little longer than one-half of disc-length; ears rather large, almost equal, with a shallow and broad byssus anteriorly, marked by a few obsolete radiating threads crossed by prominent, close-set growth-lines. Left valve flat, or very slightly convex, sculptured by fine cross-hatching (network striae) as well as narrow distant, rounded radiating riblets which are flattened and then obsolete towards base; each riblet separated by very wide and flat-bottomed interspaces; ears subequal with rather distinct radial threads on them, otherwise almost similar to the right valve.
Several isolated valves. Occurrence: Okada, Reg. No. 2649; Nisigôto, Reg. No. 2710. Dimensions (in mm.) : Height Length Depth
110 115 22.............. Right valve 90 90 15.............. " 90 90 flat.............. Left valve 64 64 flat.............. " The shell resembles P. (Patinopecten) yessoensis JAY from our northern seas, however, the radiating ribs in that shell are more prominent.
Another related form with the present new species is perhaps P. (Patinopecten) plebejus YOKOYAMA¹. What Dr. M. YOKOYAMA reported as P. plebejus from the environs of Tanagura, is perhaps this new species. The distinguishing characters of the two are: (1) in the present new species the radiating ribs are fewer and broader and with larger ears, (2) the network sculpture is more distinct in the left valve of P. plebejus than in that of P. paraplebejus.» ¹ YOKOYAMA: Journ. Fac. Sci. Imp. Univ. Tôkyô, Sec. 2, Vol. 1, Pt. 8, p. 305, pI. 36, figs. 1, 2, 1926.
SHICHIHEI NOMURA & KOTORA HATAI, 1936
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«Pecten (Patinopecten) yessoensis Jay, Nomura, 1935a, p. 105, pI. 5, fig. 5.
Pecten (Patinopecten) paraplebejus Nomura and Hatai, 1936b, p. 119, pI. 13, figs. 1,2. pI. 16, figs. 6, 7; Nomura and Hatai, 1937, p. 130, pI. 19, fig. 1. Patinopecten paraplebejus (Nomura and Hatai), Masuda, 1959a, p. 2, pI. 1, figs. 1-6. Holotype : – SM, Reg. No. 2649.
Remarks: – This species resembles Patinopecten yessoensis (Jay), but is distinguishable therefrom by the radial ribs which tend to become obsolete towards the ventral margin, more convexity of the right valve, several, fine, faint radial threads on the surface of auricles. Patinopecten tokunagai (Yokoyama) differs from paraplebejus by the greater number of radial ribs, somewhat smaller auricles and more conspicuous network on the surface of the left valve. Type locality, Geological formation and Age: – Road-side cliff, south of Okada, Tanaguramachi, Higashi-Shirakawa-gun, Fukushima Prefecture (Lat. 37°01'N., Long. 140° 26'30''E.). Kubota formation. Middle Miocene. Distribution: – Kubota and Urushikubo formations, Fukushima Prefecture; Ogane and Kanomatazawa formations, Tochigi Prefecture; Otsutsumi and Nanakita formations, Miyagi Prefecture; Ginzan formation, Yamagata Prefecture: all Middle Miocene in age. Occurrence: – Abundant in the conglomeratic coarse-grained sandstone of the Kubota formation; rare in the pebbly conglomerate of the Nanakita formation; common in the conglomeratic very coarse-grained sandstone of the Ginzan formation.» 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. 208, 209]
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«Nom. Jap., Hiraune-hotate n. n.
Pecten (Patinopecten) paraplebejus NOMURA and HATAI, Sait Hô-on Kai Mus., Res. Bull., No. 10, p. 119, pI. 13, figs. 1, 2; pI. 16, figs. 6, 7, 1936.
Locality: Matumori (rare), Reg. No. 6351.»
NOMURA, S. & K. HATAI. 1937. A List of the Miocene Mollusca and Brachiopoda Collected from the Region Lying North of the Nanakita River in the Vicinity of Sendai, Rikuzen Province, Japan. Saito Ho-on Kai Museum of Natural History Research Bulletin, 13: 121-145, pls. 17-21. [p. 130, pl. 19, fig. 1]
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Pecten (Patinopecten) paraplebejus Yokoyama; S. Nomura & K. Hatai, 1937, A List of the Miocene Mollusca and Brachiopoda Collected from the Region Lying North of the Nanakita River in the Vicinity of Sendai, Rikuzen Province, Japan, plate 19, figure 1.
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