A gastropod (Colus islandicus)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



A tall shell, up to 15 cm high and 5 cm broad, with up to 9 moderately tumid whorls that form a spire with a concave profile. Protoconch bulbous, often of greater diameter than the next whorl and set more obliquely on the spire. Numerous pronounced spiral ridges present. Outer lip arises between spiral ridges 10-12 on last whorl. Shell white with a pale-yellow horny layer overlying the calcareous matter of the shell (periostracum).

Recorded distribution in Britain and Ireland

Colus islandicus is a northern species extending south to Shetland, the north coast of Scotland and Northern Ireland. Subfossil shells may be found in more southern waters.

Global distribution

The species has a circumpolar distribution but extends south in the eastern Atlantic as far as northern Britain.


Occurs on soft substrata from 10-3000 m.

Depth range


Identifying features

  • A tall shell with a bulbous protoconch.
  • Whorls with numerous spiral ridges and covered with a periostracum.
  • Aperture with a long, narrow, almost straight siphonal canal.

Additional information

Similar to Colus gracilis but the spiral ridges are more pronounced, especially towards the apex, and the siphonal canal does not incline markedly to the left as it does in Colus gracilis. Occurrence in Britain may be adversely affected by seawater warming.

Listed by

- none -


  1. Graham, A., 1988. Molluscs: prosobranchs and pyramellid gastropods (2nd ed.). Leiden: E.J. Brill/Dr W. Backhuys. [Synopses of the British Fauna No. 2]

  2. Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins.

  3. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  4. Hiscock, K., Southward, A., Tittley, I., Jory, A. & Hawkins, S., 2001. The impact of climate change on subtidal and intertidal benthic species in Scotland. Scottish National Heritage Research, Survey and Monitoring Report , no. 182., Edinburgh: Scottish National Heritage

  5. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  6. McMillan, N.F., 1968. British Shells. London: Frederick Warne & Co Ltd.


  1. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) data for Great Britain and Ireland - restricted access. Occurrence dataset: https://doi.org/10.15468/4bsawx accessed via GBIF.org on 2018-09-25.

  2. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) records for Great Britain and Ireland. Occurrence dataset: https://doi.org/10.15468/aurwcz accessed via GBIF.org on 2018-09-25.

  3. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  4. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-06-25


This review can be cited as:

Skewes, M. 2005. Colus islandicus A gastropod. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25-06-2024]. Available from: https://marlin.ac.uk/species/detail/1655

Last Updated: 17/10/2005