Pecten plebejus Yokoyama, 1926
YOKOYAMA,
M. 1926. Fossil shells from Sado. Journal of the Faculty of Science,
Imperial University of Tokyo [Section II: Geology, Mineralogy,
Geography, Seismology], 1 (8): 249-312, pls. 32-37. [p. 305, pl. 36, figs. 1, 2]
«133. Pecten plebejus, n. sp.
PI. XXXVI. Figs. 1, 2. Shell large, thin, compressed, orbicular, inequivalve. Right valve somewhat convex, ornamented with numerous, very low, broad, flattish often unequal, radiating ribs with interspaces either equal or narrower; left valve flatter than right, with very little convexity, ornamented with small, obtuse, distant, radiating riblets with very wide intervals, the number varying from a little over ten to more than twenty and usually with a finer intercalary between; the snrface is often covered with a fine net-like ornament. Ears somewhat unequal, the anterior in both valves being somewhat larger; a shallow byssal notch is present below the anterior ear of the right valve. Very frequent at Kaidaté.
The largest right valve measures about 130 millim. in height and length, and is 15 millim. deep. Another right valve somewhat smaller in size measures about 10 millim. in height and length, and 11 millim. in depth. The largest left valve measures about 113 millim. in height and length, and about 6.5 millim. in depth, while another, a little more convex measures about 108 millim. in height and length, and 9 millim. in depth. Fossil occurrence.— Kaidaté (frequent). Upper and lower horizons, Sawané.» MATAJIRO YOKOYAMA, 1926
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M. Yokoyama, 1926, plate 36.
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