More images and detailed account at https://flic.kr/s/aHsjNKPM1L
Shell
Up to 6.5mm high. Tall spire of up to 14 whorls. Whorls flattish, but sutures quite deep. Three spiral rows of squarish tubercles, evenly spaced to give square lattice appearance, on each whorl, except four smooth apical whorls forming protoconch, and base of final whorl which has 2 or 3 inconspicuous spiral ridges (occasionally nodose). Protoconch sometimes lost. Aperture small, with basal siphonal notch, closed by operculum. Shell glossy maroon, paler in spaces between tubercles.
Body
Flesh white with grey on dorsum of head and body, yellow opercular lobe and band of yellow spots behind eye. No snout. Small black mouth between bases of tentacles is opening into introverted slender proboscis. Small thin white siphon, with black interior revealed at bifid reflexed tip, rests in siphonal notch. Siphon about as thick as thin white tentacles. Eye on thickened base of tentacle. Male lacks penis. Foot folds across middle at a transverse groove. Large circular opening of pedal gland, near centre of white sole, exudes copious mucus which can be formed into climbing rope. Anterior of foot deeply cleft into a “duckbill”.
- Tall maroon spire to 6.5mm.
- 3 spiral rows of tubercles on whorls.
- Base of final whorl lacks tubercles & has 2 or 3 spiral ridges.
- Lives at LWS and sublittorally.
- Feeds on Hymeniacidon perleve & Halichondria panicea (sponges)
Cerithiopsis barleei Jeffreys, 1867
- Spire to 7mm, paler, taller and thinner than C. tubercularis.
- 3 spiral rows of tubercles on whorls.
- Base of final whorl lacks tubercles & has no spiral ridges.
- Lives sublittorally, not on shore.
- Feeds on Suberites domunculus (sponge)
Cerithiopsis metaxa (della Chiaje, 1828)
- Very tall, almost straight sided, yellowish or whitish spire to 8mm.
- 4 spiral ridges, 3 or 4 tuberculated, on penultimate whorl.
- Base of final whorl lacks tubercles.
- Lives sublittorally, not on shore.
On shores at LWS, and sublittorally to about 100m. Specialist feeder on sponges Hymeniacidon perleve and Halichondria panicea. Long fine proboscis, when everted, inserted through sponge’s osculum, and jaws at tip loosen soft tissue which is raked back along proboscis by radula. Favours sponges on rocks with tufts of red seaweed, such as Lomentaria and Corralina. Shell colour matches that of weeds, among which it climbs with aid of mucus ropes excreted from pedal glands. Also eats epiphytic and epizooic growths on weeds. Egg capsules inserted into sponge. Veliger larvae live in plankton before settling and metamorphosing.
Norway to Azores and Black Sea (See GBIF map). Not uncommon around Britain and Ireland, except apparently absent from east coasts of Scotland and England.
The map provided here shows the distribution of the species based on Conchological Society data.
Fretter, V. and Graham, A. 1962. British prosobranch molluscs. London, Ray Society.
Graham, A. 1988. Prosobranch and pyramidellid gastropods. London.