Pecten atsumiensis Yokoyama, 1926
YOKOYAMA, M. 1926. Fossil shells from the Atsumi peninsula. Miwaka. Journal of the Faculty of Science, Imperial University of Tokyo [Section II: Geology, Mineralogy, Geography, Seismology], 1 (9): 369-375, pl. 43. [pl. 43, figs. 4, 5]
«9. Pecten atsumiensis, nov. sp.
Pl. XLIII. Figs. 4, 5. Shell rather small, moderately thick. Right valve compressed, almost as high as long, equilateral, anterior extremity roundly angulate, posterior markedly angulate, though the angle is blunt, radiately ribbed. Ribs sixteen or seventeen, straight, more or less elevated, broad, flattish on top with edges blunt and flanks very steep, separated bt flat, usualy somewhat narrower, valleys. ears comparatively large, anterior and posterior different in shape; anterior ear somewhat longer and narrower, with anterior border somewhat curved, radiately ribbed with ribs seven to ten, scaly; byssal notch very deep, pointed; posterior ear triangular with posterior border almost straight and somewhat oblique, gradually receding bellow, only with concentric lines of growth.
Three right valves, the largest measuring 46 millim. in height and length, and 8.3 in depth. This species has a close resemblance to Pecten (Equipecten) palmeri Dall (Arnold, Tert. a. Quatern. Pectens California, p. 136, pl. L, fig. 2) living in the Gulf of California, although there are some slight differences. The latter has the posterior extremity rounded and not angulate, and the posterior ear radiately costulated. Even if these differences are only variations, in the absence of the left valve it seems to be not at all prudent to treat the Japanese fossil under Dall's name. Fossil occurrence — Upper Clay, Tonami.» MATAJIRO YOKOYAMA, 1926
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M. Yokoyama, 1926, plate 43.
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