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Species / Gymnarus Yabei

Gymnarus Yabei

Stromboidea


Original description of Pugnellus (Gymnarus) yabei by Nagao, 1939

  • "Shell rather small, thin-tested; spire moderately elevated, composed of about five convex whorls with sinuous axial ribs; sutures distinct. Body whorl large, moderately inflated, very high, occupying about three-fourths of the total height, evenly convex above, contracted and elongated below. Aperture rather broad, long, acutely angulated posteriorly; anterior canal long, nearly vertical, straight, not deeply notched; inner lip slightly excavated, oblique above and almost vertical below; outer lip relatively thin, being only slightly thickened, broadly and distinctly excavated above, expanded with a・hook-like prolongation; the prolongation curved upward, terminating in an acute end, trigonal in lateral view, and crescentic in cross-section, with a ridge outside, continuing with a round angle of the body whorl which becomes obsolete in a short distance backward from the outer lip; the lower border of the prolongation slightly excavated at its origin, from this point the outer lip nearly straight downward. Callosity well developed, extending over the body whorl, and almost covering the whole ventral surface of the shell up to the apex. Surface ornamented with numerous axial ribs which are crowded, strongly sinuous, being nearly vertical on the upper part, much curved on the shoulder, where they are most prominent and form obliquely elongated strong nodes."

Locus typicus: the Itinosawa, a tributary of the Horomui-gawa; Province of Isikari, Japan

Stratum typicum: Cretaceous

References:

  • Nagao T. (1939) Some Molluscan Fossils from the Cretaceous Deposits of Hokkaido and Japanese Saghalien Part II. Gastropoda. Journal of the Faculty of Science, Hokkaido Imperial University. Ser. 4, Geology and mineralogy, 4(3-4): 213-239

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