Propeamussium tateiwai Kanehara, 1936
KANEHARA, K. 1936. Neogene shells from south Chôsen (Korea). Japanese Journal of Geology and Geography, 13 (1-2): 31-38, pI. 10. [p. 33, pl. 10, figs. 5, 6]
1936 Propeamussium (Propeamussium) tateiwai Kanehara, 1936
K. Kanehara, 1936, plate 10.
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«Propeamussium (Propeamussium) tateiwai n. sp.
(Pl X, Figs. 5, 6) Type: An example from the Ennichi Series, Chôsen; preserved in the
Geol. Inst., Fac. Sci., Imp. Univ., Tokyô. Description.
Shell small, thin, somewhat translucent, compressed, slightly inequilateral, inequivalve; as long as high, and rounded in outline with acute umbone and smooth margin. Antero- and postero-dorsal rnargins of both valves sloping, nearly straight, forming obtuse angles at anterior, and posterior ends.
Right valve: External surface with regular, concentric incised lines with nine radiating obtuse ridges. Internal surface with nine elevated radiating ridges, which, before reaching the ventral border, terminate with ends somewhat swollen. Auricles unequal in size; the posterior Iarge, with no regular ornamentation; the anterior srnall, triangular, finely ornamented with growth lines; Bissal notch distinct. Left valve : External surface with fine regular concentric incised lines and dense but indistinct radiating striae; internal surface smooth with feeble irregular concentric folds. Auricles poorely preserved on present specimen. The outer zone not so wide. Dimension.
Occurrence. Abundant.
Remarks.
Four species of Propeaumussiun have been found in Japan, namely Propeamussium clancularium (YOKOYAMA) [10], Propeamussium nakazawai KURODA [11], Propeamussium cmadoritinctum KURODA [12] and Propeamussium [13] cowperi yubarensis (YABE et NAGAO). Propeamussium clancularium (YOKOYAMA) which was described by Prof. YOKOYAMA from the Tertiary of Tôtômi, has, as well as Propeamussium cowperi yubarensis (YABE et NAGAO), seven elevated radiating ridges on the internal surface of its right valve, while the present new species has nine. Propeamussium nakazawai KURODA, which is now living in the bottom of the Gulf of Sagami, has nine radiating ridges on the internal surface of the right valve, but has shells of larger and higher ovate form than Propeamussium tateiwai. Propeamussium cmadoritinctum KURODA, wich has been reported from off Isl. Yaku, Kagoshima-ken, is distinguished from the present one in its small sizce, while the outlines of the two are very similar.
E. A. SMITH has described several species of Propeamussium from the Challenger expedition. Propeamussium torresi (SMITH) [14], now living off North Australia, and which seems to have a similar outline, is provided with twelve radiating ridges on the internal surface of the right valve. Propeamussium scitulum (SMITH) [15], now living in the seas off New Guinea, resembles the present species, but has smaller shells and larger auricles than Propeamussium tateiwai. We have three species of allied form from the Tertiary of California, namely Propeamussium clallamensis (ARNOLD) [16], P. interradiatus GABB) [17] and P. stanfordensis (ARNOLD) [18]. Propeamussium clallamensis (ARNOLD) is distinguished from the present species by its smaller size, longer hinge line, more distinct byssal notch, and stoutish concentric sculpture on the external surface of the shell. Propeamussium stanfordensis (ARNOLD), which is somewhat smaller than the present species, has ten, eleven, or twelve radiating ridges on the internal surface of the right valve. Propeamussium interradiatus GABB, whose occurrence ranges from Martinez to Tejon, California, has longer hinge lines with large posterior auricle, and shorter radiating ridges on the internal surface on the right valve. Propeamussium zoniferum DAUTZ. et BAV. [19] appears to be allied to P. tateiwai, but is smaller in size, and has wider and shallower posterior and anterior sinuses than the present new species.» [10] Joun. CoIl. Sci. Inp. Univ. Tokyo, Sec. II, Vol. I, pt. 9, p. 385, Pl. XLI, figs. 7-11
[11] Venus, Vol. 3, No. 2, Appendix p. 87, figs. 101-102. [12] Ibid., Vol. 3, No. 1, Appendix p. 77. Ibid., Vol. 2, No. 6, Appendix p. 73, figs. 81-82. [13] Sci. Rep. Tohoku Imp. Univ., Sec. Ser., Vol. IX, No. 3, p. 88, PL. XVI (1), figs. 17-19. [14] Rep. Challenger, Larnellib., p. 311, Pl. XXIII, figs. 3-3b. [15] Rep. Challenger, Lamellib., p. 312, Pl. XXIII, flgs. 4-4b. [16] U. S. Geol. Surv. Prof. Paper, 47, p. 57, PI. III, fig. 2. [17] Univ. Calif. PubI. Bull. Dept. Geol., Vol. VIII, Pl. 9, fig. 5. [18] Ibid., 47, p. 91, Pl. XXIII, fig. 4. [19] Siboga Exped. Monogr. LIIIb, Lamellib., p. 33, Pl. XXXVIII, figs. 14-17. KINJI KANEHARA, 1936
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