Epitoniidae Berry, 1910 (1812)

Opalia bicarinata

(G. B. Sowerby II, 1844)

Description:

Dimensions range from 3 mm - 18 mm high and 2 mm - 18 mm wide.
Width to height ratio: 0.67:1 ~ 01:1

Shell: sub-cylindrical, elongated, narrow; microscopic to small. Exterior colour nearly white. About 10.5 whorls, wide, flat-sided; two prominent keels in the centre of the last whorl; protoconch with ~1.5 whorls paucispiral, usually eroded; teleoconch with 9 whorls. Suture pitted, crenulated. Imperforate: umbilicus closed. 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. Intritacalx present, easily abraded. Intercostal spaces very minutely cancellated. Aperture oval, with thickened, minutely crenulated margin. Operculum horny, brown, paucispiral.

Distribution:

widely distributed throughout the Indo-Pacific region, Japan [Higo et al., 1999:219]; Philippines; Fiji, New Caledonia, Marquesas [Garcia, 2004:8]; Hawaii, Australia and Cocos-Keeling Islands [DuShane, 1988:3]; to eastern Transkei, South Africa [Kilburn 1985: 270]

Habitat:

sand, intertidal to 99 m (DuShane 1990: 8).

Etymology:

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

Type Material:

Scalaria bicarinata Sowerby, 1844: British Museum (NH). Cirsotrema attenuata Pease, 1860: Kay (1965:44) selected one of the two type specimens as lectotype: British Museum (NH) Reg. No. 1962796, and the other as paralectotype: Reg.No. 1962797 [as Nodiscala attenuata (Pease, 1860) · unaccepted] - Type Locality: Negros Island (Oriental), Philippines.. [DuShane, H., 1988b]
Holotype: NHMUK 1981042 for Opalia bicarinata (G. B. Sowerby II, 1844) - Type Locality: Dumaguete, Isl. Negroes, Philippines, 7 fms (= 13 m), in coarse black sand.. [Brown, L. & Neville, B.D., 2015]
Holotype: MNHN 4182 [as Nodiscala fusoides Jousseame, 1912] - Type Locality: Aden.. [Brown, L. & Neville, B.D., 2015]
not indicated in text [as Nodiscala bicarinata (G. B. Sowerby II, 1844)] - Type Locality: Found by Mr. Cuming in coarse black sand at seven fathoms, at Dumaguete, isle of Negros' (Philippines). [Higo, S., Callomon, P. & Goto, Y., 1999]
LECTOTYPE (here selected) : B.M.(N.H.) Reg. No. 1962796. Length, 7ÐoP

SpeciesImage

arsint.com (2023).

Opalia Nodiscala bicarinata cf.
12 mm, Mactan Island, Cebu. Dived at 50 m. Nov. 2011

Distribution

as listed in source literature

Sowerby, G. B. II. (1844).

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Plate xxxv. Fig. 113-114.

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pp: 104.

86. Sc. BiCARiNATA. (pi. XXXV. f. 113, 114.) Sow. Jun. Zool. Proc, 1844.

Original description

Sowerby, G. B. II. (1873).

Shown in text as Scalaria bicarinata G. B. Sowerby II, 1844

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Plate viii. Fig. 60a.

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Plate viii. Fig. 60b.

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Species 60. (Fig. a, b, Mus. Brit.)
SCALARIA BICARINATA.
Sca.

Sowerby, G. B. II. (1873).

Shown in text as Nodiscala attenuata (Pease, 1860)

Species Image

Plate x. Fig. 71.

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Species Image

Tryon, G.W. (1887).

Shown in text as Scalaria bicarinata G. B. Sowerby II, 1844

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Plate 17. Fig. 28.

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pp: 882.

Clessin, S. (1897).

Shown in text as Scalaria bicarinata G. B. Sowerby II, 1844

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Plate 4. Fig. 5.

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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

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Plate 10. Fig. 9-10.

DuShane, H. (1988b).

Shown in text as Nodiscala attenuata (Pease, 1860) · unaccepted

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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)

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pp: 219.

Garcia, E.F. (2004a).

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pp: 9. Fig. 22-26.

22. Marquesas Islands, Ua Huka. 8°53.6'S, 139°37'W, 20-34 m [ Sta.24bis], length 9.0 mm.
23. New Caledonia, sector de Touho. 20°52.7'S, 165°19.5'E, 5-25m [Expédition MONTROUZIER, sta. 1271], length 6.9 mm.

Species Image

pp: 9. Fig. 22-26.

24-25. Lifou, Loyalty Islands. 20°52.5'S, 167''08.rE, 5-20 m
[Atelier Lifou, sta. 1434], length 10.3 mm.
26. Dorsal view of Sowerby's type figure ( Fig. no. 1 14)

Species Image

pp: 9. Fig. 26.

22-26. Opalia bicarinata (Sowerby, 1844).
26. Dorsal view of Sowerby's type figure ( Fig. no. 1 14)

arsint.com (2023).

Species Image

Opalia Nodiscala bicarinata cf.
12 mm, Mactan Island, Cebu. Dived at 50 m. Nov. 2011

Species Image

Synonymy:

Cirsotrema attenuatum Pease, 1861 [in Kay, E.A., 1965].
Nodiscala attenuata (Pease, 1860) [in Sowerby, G. B. II., 1873].
Nodiscala attenuata (Pease, 1860) · unaccepted [in DuShane, H., 1988b].
Nodiscala bicarinata (G. B. Sowerby II, 1844) [in Higo, S., Callomon, P. & Goto, Y., 1999].
Nodiscala fusoides Jousseame, 1912 [in Brown, L. & Neville, B.D., 2015].
Nodiscala fusoides Jousseaume, 1912 [in Jousseaume, F., 1912].
Opalia fusoides (Jousseaume) [in Kaicher, S.D., 1981].
Scalaria bicarinata G. B. Sowerby II, 1844 [in Clessin, S., 1897].
Scalaria bicarinata G. B. Sowerby II, 1844 [in Sowerby, G. B. II., 1873].
Scalaria bicarinata G. B. Sowerby II, 1844 [in Tryon, G.W., 1887].

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]
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]
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. (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. (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
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]
Sowerby, G. B. II. (1873). Monograph of the genus Scalaria. Conchologia iconica, or illustrations of the shells of molluscous animals, vol. 19, pls 1-16 and unpaginated text.. 19. London. https://www.biodiversitylibrary.org/page/8217819 [Accessed 24 August 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 [Accessed 8 November 2025]

WoRMS direct page link: Open WoRMS record