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Epitoniidae Berry, 1910 (1812)

Opalia bicarinata

(G. B. Sowerby II, 1844)

Description:

Dimensions range from 3 mm - 18.2 mm high and 2 mm - 18 mm wide.
Width to height ratio: 0.67:1 ~ 0.99:1

Shell: sub-cylindrical, elongated, narrowly acuminate, often deformed; solid, rather thick; microscopic to small. Exterior colour nearly white, dull greyish white. About 12.5 whorls, wide, flat-sided, moderately convex, not angular; two prominent. nodulous keels in the centre of the last whorl ; protoconch with ~1.5 whorls paucispiral, usually eroded; teleoconch with 9-11 whorls with coarse axial ribs overlapping the suture, rather flattened. Spire obtuse. Suture fairly deep, pitted, crenulated, somewhat constricted. Imperforate: umbilicus closed. Approximately 8 - 10 costae on the body whorl. Costae are coarse axial ribs overlapping the sutures and forming crenulations. There is a single varix on each whorl. The varix is two keels appear becoming nodulose on the last whorl. Costae not continuous; nodulous at the suture. Intritacalx present, bearing microscopically pitted spiral striae, easily abraded. Intercostal spaces very minutely cancellated. Base without a basal disk. Aperture oval, with thickened, minutely crenulated margin; peristome complete; outer lip thickened and somewhat reflected with faintly crenulate margin. Operculum horny, brown, paucispiral.


Distribution:

Cocos Keeling Islands & Hawaii; Hawaii and Red Sea to eastern Transkei.; throughout tropical Indo-Pacific from Hawaii, Philippines, Japan, Red Sea to South Africa [Nakayama, 2003:81]; widely distributed throughout the Indo-Pacific region [DuShane, 1988b: 3]; Japan [Higo et al., 1999:219]; Philippines; Fiji, New Caledonia, Marquesas [Garcia, 2004:8]; Hawaii, Australia [DuShane, 1988b:3]; Cocos-Keeling Islands [Maes, 1967:117] ; Suez, Aden [Jousseaume, 1912:238] to eastern Transkei, South Africa [Kilburn 1985: 270].


Habitat:

Subtidal, sand, intertidal to 99 m [DuShane 1990: 8], 5-20 m, sand [Higo et al., 1999:219].


Etymology:

[latin] from bi = two and carinatus = having a keel shaped ridge, in reference to the two keels on the body whorl.


Type Material:

DuShane [1990:7] noted that Cernohorsky, in Tropical Marine Shells, vol. 3 [1978:168], appeared to be the first to recognise the synonymy of Opalia bicarinata and O. attenuata, a view later shared by Garcia [2004a:8]. Kilburn [1985:296] and Garcia [2004a:8] both reported the holotype of Opalia bicarinata (G. B. Sowerby II, 1844) as lost. However, Brown & Neville [2015:44] cited the holotype as NHMUK 1981042.
A search of the Natural History Museum's online catalogue located two separate specimen records, NHMUK 198142 and NHMUK 1981042, both designated as the holotype [Natural History Museum, 2014: ZOO.198142; ZOO.1981042].
For Cirsotrema attenuatum Pease, 1860, Kay [1965:44] designated BMNH 1962796 as the lectotype and BMNH 1962797 as the paralectotype.

Holotype: MNHN 4182 [as Nodiscala fusoides Jousseame, 1912] - Type Locality: Aden.. [Brown & Neville, 2015: 75]
Holotype: NHM: 198142 for Opalia bicarinata (G. B. Sowerby II, 1844) - Type Locality: Dumaguete, I. of Negros. [Natural History Museum, 2014: 198142]
Holotype: NHM: 1981042 for Opalia bicarinata (G. B. Sowerby II, 1844) - Type Locality: Dumaguete, I. of Negros. [Natural History Museum, 2014: 1981042]
Paralectotype: NHM: 1962797 [as Cirsotrema attenuatum Pease, 1860] - Type Locality: Sandwich Islands. [Natural History Museum, 2014: 1962797]
Lectotype: NHM: 1962796 [as Cirsotrema attenuatum Pease, 1860] - Type Locality: Sandwich Islands. [Natural History Museum, 2014: 1962796]


SpeciesImage

Natural History Museum (2014). Fig. ZOO: 198142.

Holotype: NHM ZOO: 198142
Dumaguete, I. of Negros
The Trustees of the Natural History Museum, London

Distribution

as listed in source literature

Sowerby, G. B. II. (1844).
Species Image
Plate xxxv. Fig. 113-114.
Species Image
pp: 104.
86. Sc. BiCARiNATA. (pi. XXXV. f. 113, 114.) Sow. Jun. Zool. Proc, 1844.

Original description
Pease, W. H. (1861).
Species Image
pp: 400.
Reeve, L.A. (1873).
Shown in text as Scalaria bicarinata G. B. Sowerby II, 1844
Species Image
Plate viii. Fig. 60a.
Species Image
Plate viii. Fig. 60b.
Species Image
Species 60. (Fig. a, b, Mus. Brit.)
SCALARIA BICARINATA.
Sca.
Reeve, L.A. (1873).
Shown in text as Nodiscala attenuata (Pease, 1860)
Species Image
Plate x. Fig. 71.
Species Image
Species Image
Tryon, G.W. (1887).
Shown in text as Scalaria bicarinata G. B. Sowerby II, 1844
Species Image
Plate 17. Fig. 28.
Species Image
pp: 882.
Clessin, S. (1897).
Shown in text as Scalaria bicarinata G. B. Sowerby II, 1844
Species Image
Plate 4. Fig. 5.
Species Image
pp: 15.
Shell small, subcylindrical, imperforate, whitish, narrow, very finely cancellated; spire elevated, blunt; whorls laterally nearly straight and tapering; last whorl rather short, strongly bicarinate, pitted above; aperture small, nearly square.
Kay, E.A. (1965).
Shown in text as Cirsotrema attenuatum Pease, 1861
Species Image
Plate 10. Fig. 9-10.
DuShane, H. (1988b).
Shown in text as Nodiscala attenuata (Pease, 1860) · unaccepted
Species Image
pp: 3.
Opalia bicarinata (Sowerby, 1844), Kapahoi, Ha-waii. Collected by Goldsmith March 1983. DuShane Collection. Sizes: 4.5 by I.1 mm; 3 by I mm.
Higo, S., Callomon, P. & Goto, Y. (1999).
Shown in text as Nodiscala bicarinata (G. B. Sowerby II, 1844)
Species Image
pp: 219.
Nakayama, T. (2003).
Shown in text as Opalia (Nodiscala) attenuata (Pease, 1860)
Species Image
pp: 105. Plate 1. Fig. 16-17.
Opalia (Nodiscala) attenuata (Pease, 1860)
height 9.4 mm; breadth 2.8 m (NA)
Garcia, E. F. (2004a).
Species Image
pp: 9. Fig. 26.
Opalia bicarinata (Sowerby, 1844).
Dorsal view of Sowerby's type figure ( Fig. no. 114)
Natural History Museum (2014).
Species Image
Fig. ZOO: 198142.
Holotype: NHM ZOO: 198142
Dumaguete, I. of Negros
The Trustees of the Natural History Museum, London

Synonymy:

Cirsotrema attenuatum Pease, 1860 [Brown & Neville, 2015: 41; Pease, 1861: 400; Kay, 1965: 44; Natural History Museum, 2014: 1962797; Natural History Museum, 2014: 1962796]
Nodiscala attenuata (Pease, 1860) [DuShane, 1988b: 3; Reeve, 1873: pl. 10, fig. 71; Jousseaume, 1912: 238; Higo et al., 1999: G1807]
Nodiscala bicarinata (G. B. Sowerby II, 1844) [Higo et al., 1999: G1806]
Nodiscala fusoides Jousseaume, 1912 [Brown & Neville, 2015: 75; Jousseaume, 1912: 240]
Opalia (Nodiscala) attenuata (Pease, 1860) [Kilburn, 1985: 270; Nakayama, 2003: 81; Kay, 1979: 157]
Opalia attenuata (Pease, 1860) [Kaicher, 1980: EP1-2290]
Opalia fusoides (Jousseaume, 1912) [Kaicher, 1981: EP2-3052]
Scalaria attenuata Pease, 1860 [Clessin, 1897: 17; Tryon, 1887: 82; Maes, 1967: 117]
Scalaria bicarinata G. B. Sowerby II, 1844 [Sowerby, 1844: 104; Reeve, 1873: pl. 8, fig. 60a-b; Clessin, 1897: 15; Tryon, 1887: 882; Kilburn, 1985: 296]


Source Literature:

arsint.com (2023). Shells for Sale:Epitonidae. arsint.com. http://www.arsint.com/seashells_epitoniidae_opalia.html [Accessed 21 October 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]
Clessin, S. (1897). Die Familie der Scalariidae. In W. Kobelt (Ed.), Systematisches Conchylien-Cabinet von Martini und Chemnitz. Neu herausgegeben und vervollständigt. 2(13). Bauer & Raspe, NürnbergBauer & Raspe, Nürnberg. https://www.biodiversitylibrary.org/page/34259905 [Accessed 21 June 2025]
DuShane, H. (1988b). Hawaiian Epitoniidae pt.1. Hawaiian Shell News. 36(2). https://www.conchology.be/?t=5002&year=1988&volume=2&hsn=10336 [Accessed 16 September 2023]
DuShane, H. (1990). Hawaiian Epitoniidae. Hawaiian Shell News. 38(Sup.1). Hawaiian Malacological Society
Garcia, E. F. (2004a). New records of Opalia-like molluscs from the Indo-Pacific, with descriptions of fourteen new species. Novapex. 5(1). http://biodiversitylibrary.org/page/42323212 [Accessed 12 September 2023]
Heros V., Lozouet, P., Maestrati, P., von Cosel, R., Brabant D., & Bouchet P (2007). Mollusca of New Caledonia. in: Payri C.E. Richer de Forges B. (Eds.) Compendium of marine species of New Caledonia, Doc. Sci. Tech.. II7 2ed. https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers15-04/010038859.pdf [Accessed 28 February 2026]
Higo, S., Callomon, P. & Goto, Y. (1999). Catalogue and Bibliography of the Marine Shell-Bearing Mollusca of Japan.. https://www.researchgate.net/publication/266375656_Catalogue_and_Bibliography_of_the_Marine_Shell-Bearing_Mollusca_of_Japan [Accessed 25 July 2025]
Huang, C. W. & Lee, Y.C. (2016). Checklist of the family Epitoniidae (Mollusca: Gastropoda) in Taiwan with description of a new species and some new records. Biodiversity Data Journal. 4. doi: 10.3897/ BDJ.4.e5653 [Accessed 25 August 2023]
Jousseaume, F. (1912). Faune malacologique de la Mer Rouge. Scalidae. Mémoires de la Société Zoologique de France.. 24(3-4). Mémoires de la Société Zoologique de France.. https://www.biodiversitylibrary.org/page/10095979 [Accessed 1 March 2025]
Kaicher, S.D. (1980). Epitoniidae I [Pack 23]. S. D. Kaicher, St. Petersburg, Florida. http://www.femorale.com/kaicher/species.asp?f=Epitoniidae&c=125 [Accessed 8 May 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]
Kay, E. A. (1979). Hawaiian marine shells: Reef and shore fauna of Hawaii section 4. Bernice P. Bishop Museum Special Publication. 64(4). Bishop Museum Press.. https://openlibrary.org/books/OL4750994M/Hawaiian_marine_shells [Accessed 24 July 2026]
Kay, E.A. (1965). Marine Molluscs in the Cuming Collection, British Museum (Natural History) Described by William Harper Pease. Bulletin of the British Museum (Natural History). Zoology Series, supplement 1. https://www.biodiversitylibrary.org/item/156261 [Accessed 12 November 2025]
Kilburn, R.N. (1985). The family Epitoniidae (Mollusca: Gastropoda) in southern Africa and Mozambique. Annals of the Natal Museum. 27(1). Natal Museum
Maes, V. O. (1967). The Littoral Marine Mollusks of Cocos-Keeling Islands (Indian Ocean). Proceedings of the Academy of Natural Sciences of Philadelphia. 119. Academy of Natural Sciences. https://www.jstor.org/stable/4064613 [Accessed 25 October 2025]
Nakayama, T. (2003). A Review of Northwest Pacific Epitoniids. Monographs of Marine Mollusca. 6. Backhuys Publishers
Natural History Museum (2014). Collection specimens [Data set]. Natural History Museum. https://doi.org/10.5519/0002965 [Accessed 6 April 2026]
Pease, W. H. (1861). Descriptions of seventeen new species of marine shells, from the Sandwich Islands. Proceedings of the Zoological Society of London. 28. Zoological Society of London. https://www.biodiversitylibrary.org/item/46225 [Accessed 15 March 2025]
Reeve, L. A. (1873). Monograph of the genus Scalaria. Conchologia iconica, or illustrations of the shells of molluscous animal. 19. London. https://www.biodiversitylibrary.org/page/8217819 [Accessed 24 August 2023]
Sowerby, G. B. II. (1844). Monograph of the genus Scalaria.. Thesaurus conchyliorum, or monographs of genera of shells.. 1 (4). London, privately published.. http://biodiversitylibrary.org/page/11076419 [Accessed 22 June 2023]
Tryon, G.W. (1887). Manual of conchology, structural and systematic with illustrations of the species. IX. Academy of Natural Sciences. https://www.biodiversitylibrary.org/page/11026889 [Accessed 20 September 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 at VLIZ. [Accessed 8 November 2025]

WoRMS direct page link: Open WoRMS record