kagamianus hokkaidoensis Kanno, 1962
KANNO, S. 1962. Molluscan fauna from the so-called Setana Formation, southwestern Hokkaido, Japan. Science Reports of the Tokyo Kyoiku Daigaku [Section C -Geology, Mineralogy and Geography], 8 (73): 49-62, pls. 1-5. [p. 57, pl 1, figs. 1-6; pl. 2, figs. 1-6]
«Patinopecten kagamianus hokkaidoensis KANNO, n. subsp.
PI. I, Figs. 1-6; PI. II, Figs. 1-6.
Nanaochlamys notoensis, MASUDA, 1960, Sci. Rep. Tohoku Univ., ser. 2, Spec. Vol., no. 4, pp. 373-375, pI. 39, fig. 1.
Shell large, moderately thick, compressed, orbicular in outline, equilateral except for auricles, right and left valves equiconvex; both valves radially ribed and forming an angle of about 115° at apex.
Right valve with 8-19 radial ribs which are strong, broadly rounded, rather flat-topped on individuals with few radials and round-topped on those with many radials; provided with radial riblets on their back and in interspaces of radials; they appear at about one-third from beak and tend to become distinct ventraly; radial ribs much broader than their interspaces on shells with fe\v radials while nearly equal on those with many radials; radial ribs at extreme lateral portions nearly flat, slender and weak in latter case; interspaces between radial ribs rather shallow, flat-bottomed on shells with few radials and rather deep and round-bottomed on those with many radials, and smooth near upper one-third. of disc whereas fine riblets appear towards ventral margin; anterior auricle sculptured with several weak radial threads and concentric growth lines, and with rather wide and shallow byssal notch with ctenolium on somewhat younger individuals, ctenolium disappear in the adults; posterior auricle similar to the anterior in sculpture; hinge line straight, almost half of shell length; hinge with wide, rather deep resilial pit with distinct lateral ridges, and simple cardinal crura. Left valve with 9-20 elevated, round-topped radial ribs separated by interspaces broader than the radials in width; individuals with many radials have several intercalaries which are somewhat weaker than other radials; surface sculptures similar to right valve; anterior auricle little larger than posterior. Interior surface of both valves somewhat folded corresponding to external sculpture. Measurement: Shown in Tables 3, 4. Comparison: Patinopecten kagamianus kagamianus (YOKOYAMA) 1932, P. k. moniwaensis MASUDA, 1958, P. k. nimaensis MASUDA are closely related to some forms of the present subspecies, but the formers differ from the latter by having smaller apical angle and restricted number of radials (see Table 5).
Remarks: Patinopecten kagarnianus (YOKOYAMA) was first reported by M. YOKOYAMA (1923) from the Kimachi formation at Kagami, Kimachi-mura, Yatsukagun, Shimane Prefecture. Recently, K. MASUDA revised P. kagamianus and its allied species and divided it into four subspecies, namely, P. kagamianus kagamianus, P. k. moniwaensis, P. k. nimaensis, and P. k. permirus. These four subspecies are thought by him to be allopatric forms from the geographic distribution and fossil occurrence. Locality and geological horizon: The cliffs of Meppu-River and Hidarimata-River near the Kaigara Bridge, Meppu, Imagane-machi. Meppu sandstone member of the Yakumo formation (Miocene).»
SABURO KANNO, 1962
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S. Kanno, 1962, plates 1, 2.
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