information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

Spotted cowrie (Trivia monacha)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.
Only coastal and marine records shown



This species has a thickly calcified, glossy shell, with closely spaced transverse ridges. The shell is up to 12 mm long by 8mm wide. The upper surface is reddish-brown in colour with 3 diagnostic spots.The underside of the shell is flattened and white. The head, tentacles, foot and mantle are brightly coloured, from yellow, red, orange and brown, the foot often being paler. When the animal is active the mantle almost completely obscures the shell, and the mantle edge draws out anteriorly into a long siphon. The shell aperture is narrow, running the whole length of the shell, turned left at the ends with both sides ridged.

Recorded distribution in Britain and Ireland

This species is widely distributed, mainly around the west coast of Britain and Ireland.

Global distribution



Trivia monacha is found on the lower shore and sublittorally on rocky coasts associated with its prey, colonial sea squirts.

Depth range


Identifying features

  • Oval, glossy shell with marked ridges on surface.
  • Shell up to 12 mm x 8 mm.
  • Long , narrow aperture.
  • Upper shell surface is reddish-brown with 3 brown spots.
  • Underside of shell is flattened and white.
  • Mantle wraps around almost entire shell when animal is active.
  • Head, tentacles, foot and mantle brightly coloured from yellow, red, orange and brown.

Additional information

Trivia monacha can be confused with Trivia arctica, the former being larger and having 3 distinctive brown spots on its shell. There is no operculum present, and the females have an additional ventral pedal gland. This species feeds on the ascidians Botryllus schlosseri, Botrylloides leachi, and Diplosoma listerianum. Breeding occurs in late spring and summer. The female deposits flask-shaped egg capsules (each containing 800 eggs), in holes that have been eaten out of the ascidian. After a few weeks the larva emerge and are free swimmming for a few months. Juveniles (5 mm long) have a short spire, wide aperture and lack the characteristic ridging of mature adults.

Listed by

- none -

Further information sources

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  1. Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Cambridge: Cambridge University Press.

  2. Gibson, R., Hextall, B. & Rogers, A., 2001. Photographic guide to the sea and seashore life of Britain and north-west Europe. Oxford: Oxford University Press.

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

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

  5. Hayward, P.J. & Ryland, J.S. (ed.) 1995a. The marine fauna of the British Isles and north-west Europe. Volume 2. Molluscs to Chordates. Oxford Science Publications. Oxford: Clarendon Press.

  6. 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.]

  7. JNCC (Joint Nature Conservation Committee), 1999. Marine Environment Resource Mapping And Information Database (MERMAID): Marine Nature Conservation Review Survey Database. [on-line]

  8. National Biodiversity Network (NBN) Atlas website. Available from:  Accessed 01 April 2017

  9. Naylor, P., 2000. Marine Animals of the South West. Plymouth: Sound Diving Publications

  10. Picton, B.E. & Costello, M.J., 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. [CD-ROM] Environmental Sciences Unit, Trinity College, Dublin.

  11. Seaward, D.R., 1982. Sea area atlas of the marine molluscs of Britain and Ireland. Peterborough: Nature Conservancy Council.


This review can be cited as:

Rowley, S.J. 2008. Trivia monacha Spotted cowrie. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 17-08-2018]. Available from:

Last Updated: 08/05/2008