Pecten plicicostulatus Matsumoto, 1930
MATSUMOTO, H. 1930. On the Marine Faunae of Three Fossil Zones of the Upper Miocene of Natori District, Province of Rikuzen. The Science Reports of the Tōhoku University [2nd. Series -Geology], 13 (3): 96-109, pls. 39, 40. [p. 105, pl. 40, fig. 15]
«Pecten plicicostulatus, sp. nov.
PI. XL (11), Fig. 15. Shell large, rather thin-valved, flattened, sligthtly inequivalve, the right valve appearing to be less flattened than the left, equilateral, subcircular, slightly shorter than wide; ribs some sixteen in number in the typical form; those of the right valve are very stout, median ones being stouter than the submarginal, much wider than interstices, broadly rounded, every two coupling so as to approximate each other and finally unite together towards the beak, divided into five to eight very fine riblets by a group of very fine grooves, with the exception of the submarginal ribs, in which the fine riblets and fine grooves are fewer; those of the left valve are narrower than interstices, rather angular, being divided into about three riblets by usually two fine grooves; ears probably subequal; shallow byssal notch appearing to be present on the right valve; the
posterior ear observed in a right valve is provided with riblets; the outer surface is very finely concentrically striated; the inner surface is folded, corresponding to the ribs and interstices of the outer. One right valve at hand measures 75 mm. in length, 78 mm. in width, 9 mm. in convexity and 37 mm. in the length of two ears. As shown by some other less complete specimens, the present species appears to become about one and a half time as large as the specimen just measured in the adult. Frequent.» HIKOSHICHIRÔ MATSUMOTO, 1930
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H. Matsumoto, plate 40.
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