Parvamussium intuscostatum (Yokoyama, 1920)
YOKOYAMA, M. 1920. Fossils from the Miura Peninsula and its inmediate North. Journal of the College of Science, Imperial University of Tokyo, 36 (6): 1-193, pls. 1-19. [p. 156, pl. 13, figs. 9, 10]
1920 Pecten intuscostatus Yokoyama, 1920
1960 Parvamussium (Polynemamussium) uschacovi Scarlato, 1960
1960 Parvamussium (Polynemamussium) uschacovi Scarlato, 1960
M. Yokoyama, 1920, plate 13.
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«Shell small, thin, compressed, nearly equivalve, equilateral, nearly round, with antero-dorsal and postero-dorsal margins sloping, straight or slightly concave and forming obtuse angles at anterior and posterior ends. Surface with fine dense concentric lines. Inner surface with about sixteen distant radial riblets, most distinct near the ventral margin, at a little distance from which they are somewhat thicker and knot-like. Ears very unequal, the anterior being the largest; they are also unequal in both valves, those of the right being much larger than those of the left. They are all ornamented with radial sealy riblets, except the posterior ear of the left valve, which is very small and smooth. Byssal notch distinct.
A perfect specimen with bolh valves from Kami-Miyata measures 11 millim. in length and height, and 3 millim. in thickness. A single. val ve (right?) from KOSHIBA which I described as Pecten similis LASKY (Proc. Geol. Soc. Tokyo, vol. XXVIII, no. 208, p. 3, pI. I, fig. 1) is, as I am now convinced, an imperfectly preserved specimen of this species. A young specimen of the left valve from Shimo-Miyata, only 5,5 millim. high does not show the radial riblets of the inner surface. This species resembles Pecten distinctus SMITH (Challenger Lamellibr., p. 304, pI. XXII, fig. 3) in form, but the latter has the radiating striae on the surface, while the internal costulae are wanting. Fossil occurrence.— Miyata Zone (Shimo-Miyata and Kami-Miyata); Koshiba Zone (Koshiba). Upper Musashino of Kazusa.» MATAJIRO YOKOYAMA, 1920
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«Parvamussium intuscostatum (Yokoyama, 1920).
Pecten intuscostatum Yokoyama 1920; Parvamussium (Polynemamussium) uschakovi Scarlato 1960.
Type locality: Japan. Distribution: Aleutian Islands; Northwest Pacific; depth unknown.
Remarks: Specimens of P. uschakovi from the Aleutian Islands were identified by Paul Scott and are housed at the Santa Barbara Museum of Natural History (Clark⁴).» ⁴ Clark, R. N. 2012. Personal commun. Insignis Biological Consulting, Eagle Mountain, Utah 84005.
DRUMM, D. T., K. P. MASLENIKOV, R. V. SYOC, J. W. ORR, R. R. LAUTH, D. E. STEVENSON & T. W. PIETSCH. 2016. An annotated checklist of the marine macroinvertebrates of Alaska. NOAA Professional Paper NMFS, 19: 1-289. [p. 143]
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