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Taxon profile

species

Tropidomarga biangulata Powell, 1951

kingdom Animalia - animals »  phylum Mollusca - mollusks »  class Gastropoda - gastropods »  order Trochida »  family Turbinidae - Turbans and Star Shells »  genus Tropidomarga

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Tropidomarga biangulata

Author: Powell

Tropidomarga biangulata

Author: Engl, W.

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Description

Shell of moderate size, depressed-conical, with prominently shouldered spire-whorls and biangulate body-whorl, broadly umbilicated and sculptured with numerous spiral lirations crossed by dense retractive axial threads. Whorls six, including a low rounded protoconch of one smooth whorl. First post-nuclear whorl with two spiral Iirae, second with six, body-whorl with twelve lirations between the suture and upper angulation, nine between the upper and lower angulations (about fifteen, angulations, included) and about thirty on the base. They continue just over the edge of the umbilicus, but the remainder of the surface of the walls of the steep-sided umbilicus is plain. Umbilicus about one-fifth major diameter of the base. The suture is delicately crenulatcd by the axial threads. The angulations are broadly rounded and do not interrupt the sculpture.
Aperture rhomboidal, outer lip thin, strongly retractive in profile, inner lip inclined but moderately straight, slightly thickened medially and slightly encroaching upon the umbilicus, where it curves above and finally spreads as a very thin nacreous glaze over the parietal wall. This glaze is so thin that it does not obliterate the spiral sculpture. Colour buff to very light brown above, creamy white on the base and iridescent within the aperture. Operculum horny, thin, yellowish brown, circular and multispiral.
The biangulate whorls give the species a superficial resemblance to Strebels Margarella tropidophoroides.
Powell, 1951. Antarctic and Subantarctic Mollusca: Pelecypoda and Gastropoda. (Original description)
Author: Jan Delsing

Links and literature

EN Galli C.: WMSDB - Wolrdwide Mollusc Species Data Base July 10, 2013 [http://www.bagniliggia.it/WMSD/WMSDhome....] [as Tropidomarga biangulata Powell, 1951]
Data retrieved on: 22 November 2013

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