Epitoniidae Berry, 1910 (1812)

Epitonium tacitum

(Iredale, 1936)

Description:

Dimensions range from 7.42 mm - 25 mm high and 3.55 mm - 9 mm wide.
Width to height ratio: 0.48:1 ~ 0.36:1

Shell: slender, elongate; moderately thin; small to moderately small. Exterior colour white, dull white. About 11 whorls, rounded, disconnected, joined only by costae; teleoconch with 8-11 whorls well rounded. Suture very deep. Umbilicate: closed by basal rib, may be slightly open. Approximately 6 - 12 costae on the body whorl. Costae are erect, about as wide as high, not lamellar. Costae aligned from whorl to whorl; not peaked; rolled back edge, somewhat folded back; continuous from whorl to whorl. Intercostal spaces with spiral threads, crossed by microscopic axial striae creating a lattice appearance. Base costae terminate in a coarse rib at the fasciole. Aperture round, ovate; peristome lips just meeting to form a complete free peristome; outer lip with normal costa externally. Operculum corneous.

Should not be confused with Epitonium minorum (Iredale, 1936), being easily separated by its less prominent lamellae and the fine latticed ornament of the interstices [Macpherson & Gabriel, 1962:117]

Distribution:

Darwin, NT, around northern Australia to Bermagui, NSW [Beechey, 2008], Macpherson & Gabriel [1962:117] also cite records from Western Port, Victoria, Wilson [1993:379] extends the range to southern Western Australia

Habitat:

Intertidal to 10m. Most specimens obtained from beach wash up [Beechey, 2008]

Etymology:

[latin] from tacitus = silent or reserved, may imply something quiet, discreet, hidden, or not overtly expressed. This may be in relation to the obscure interstitial sculpture which may be easily overlooked.

Type Material:

Holotype: AMS C.60643 [as Laeviscala tacita Iredale, 1936] - Type Locality: Sydney Harbour, New South Wales, Australia.. [Brown, L. & Neville, B.D., 2015]

SpeciesImage

Iredale, T. (1936). Plate xxii. Fig. 5.

with detail of intercostal sculpture

Distribution

as listed in source literature

Iredale, T. (1936).

Species Image

Plate xxii. Fig. 5.

with detail of intercostal sculpture

Species Image

pp: 297. Plate xxii.

original description

Macpherson, J.H. & Gabriel, C.J. (1962).

Species Image

pp: 117.

Species Image

pp: 118.

Wilson, B.R. (1993).

Species Image

pp: 379. Fig. 11.

Beechey, D. (2008).

Species Image

pp: Epitonium tacitum. Fig. 1.

Port Stephens, NSW Australian Museum: C.345617

Synonymy:

Laeviscala tacita Iredale, 1936 [in Brown, L. & Neville, B.D., 2015].

Source Literature:

Beechey, D. (2008). Shells NSW -Epitonium_tacitum. https://seashellsofnsw.org.au/Epitoniidae/Pages/Epitonium_tacitum.htm [Accessed 9 May 2023]
Bonfitto, A. (2018). New species of Epitoniidae (Gastropoda: Epitonioidea) from the Red Sea. Molluscan Research. 38:2. Taylor 7 Francis. https://doi.org/10.1080/13235818.2017.1385168 [Accessed 26 August 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]
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]
Macpherson, J.H. & Gabriel, C.J. (1962). Marine Molluscs of Victoria. Melbourne University Press and National Museum of Victoria: Melbourne.. https://archive.org/details/marinemolluscsof0000jhop/page/118/mode/2up [Accessed 13 June 2025]
Weil, A., Brown, L. & Neville, B. (1999). The Wentletrap Book. Evolver
WoRMS Editorial Board (2025). World Register of Marine Species. https://www.marinespecies.org [Accessed 8 November 2025]

WoRMS direct page link: Open WoRMS record