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Epitoniidae Berry, 1910 (1812)

Opalia apostolorum

(Iredale, 1936)

Description:

Dimensions range from 7 mm - 9 mm high and 2 mm wide.
Width to height ratio: 0.29:1 ~ 0.22:1

Shell: tall, slender with blunt apex; minute to small. Exterior colour fawn, whitish. About 7 whorls, weakly rounded; protoconch with ~1 whorls stout, incurved, smooth; teleoconch with ~6 whorls. Imperforate: umbilicus closed. Approximately 10 - 12 costae on the body whorl. Costae are rounded, sinuous, flattened at the suture, resting on the base of the preceding whorl. Costae aligned from whorl to whorl; Intritacalx present, chalky, pitted, entire surface densely sculptured with microscopic pits in a square pattern. Intercostal spaces overridden by fine threads. Base strong basal keel present, bicarinate, [with 2 ridges]. Aperture elongate oval, lip as a large flattened varix.

Nodiscala subcrassa (Cotton & Geoffrey, 1938) from SA may be the same species.


Distribution:

Known only from holotype and paratype, both dredged between Balls Head and Goat Island, Port Jackson, NSW [Beechey, 2008]


Habitat:

offshore species


Etymology:

[latin] apostolorum = of the apostles. Iredale did not give his reasons for the naming of the species


Type Material:

Dredged off Ball's Head, Sydney Harbour. for Opalia apostolorum (Iredale, 1936). [Iredale, T., 1936]
holotype: AMS C.7863 [as Nodiscala apostolorum Iredale, 1936:] - Type Locality: off Ball's Head, Sydney Harbour, New South Wales, Australia.. [Brown, L. & Neville, B.D., 2015]


SpeciesImage

Iredale, T. (1936). Plate xxii. Fig. 27.

Distribution

as listed in source literature

Iredale, T. (1936).
Species Image
Plate xxii. Fig. 27.
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pp: 304.
original description
Kaicher, S.D. (1981).
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Card #: EP2-3132.
Holotype: C-7863, Australian Museum
Wilson, B.R. (1993).
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pp: 379. Fig. 29a-b.
Beechey, D. (2008).
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pp: Opalia apostolorum. Fig. 1.
Holotype: dredged between Balls Head and Goat Island, Port Jackson, NSW (C.007868)

Synonymy:

Nodiscala apostolorum Iredale, 1936: [in Brown, L. & Neville, B.D., 2015].


Source Literature:

arsint.com (2023). Shells for Sale:Epitonidae. arsint.com. http://www.arsint.com/seashells_epitoniidae_opalia.html [Accessed 21 October 2023]
Beechey, D. (2008ad). Opalia_apostolorum. Seashells of NSW. https://seashellsofnsw.org.au/Epitoniidae/Pages/Opalia_apostolorum.htm [Accessed 10 May 2023]
Brown, L. & Neville, B.D. (2015). Catalog of the recent taxa of the families Epitoniidae and Nystiellidae (Mollusca: Gastropoda) with a bibliography of the descriptive and systematic literature. Zootaxa. 3907(1). Magnolia Press Auckland, New Zealand. http://dx.doi.org/10.11646/zootaxa.3907.1.1 [Accessed 22 October 2023]
Cotton, B.C. & Godfrey, F.K. (1938). New Species of South Australian Gastropoda. Records of the South Australian Museum. 6. Published under the authority of the board of governors and edited by the museum director. https://www.biodiversitylibrary.org/page/41025870 [Accessed 3 June 2025]
Hutchings, P. & Ahyong, S. & Ashcroft, M. & Mcgrouther, Mark & Reid, A. (2013). Sydney Harbour: its diverse biodiversity. Australian Zoologist. 36. http://dx.doi.org/10.7882/AZ.2012.031 [Accessed 28 February 2026]
Iredale, T. (1936). Australian molluscan notes. No. 2.. Records of the Australian Museum. 19(5). Australian Museum, Sydney. doi:10.3853/j.0067-1975.19.1936.704 [Accessed 14 September 2023]
Kaicher, S.D. (1981). Epitoniidae II [Pack 30]. S. D. Kaicher, St. Petersburg, Florida. http://www.femorale.com/kaicher/species.asp?f=Epitoniidae&c=125 [Accessed 8 May 2023]
Weil, A., Brown, L. & Neville, B. (1999). The Wentletrap Book. Evolver
Wilson, B.R. (1993). Australian Marine Shells. Australian Marine Shells. 1. Odessey Publications
WoRMS Editorial Board (2025). World Register of Marine Species. https://www.marinespecies.org [Accessed 8 November 2025]

WoRMS direct page link: Open WoRMS record