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Usual length to 10 mm
, width to 6 mm. Flexible, varies between flat [image3]
and upturned saucer 
. Body dorsum nearly smooth, with a few small tubercles 
. Ground colour 
of dorsal surface light sandy brown, yellowish, or off-white. Surface usually has small black or sepia flecks 
that mimic small inhalent pores on compound ascidians such as Trididemnum
). Also markings of various colour, including pure white, ochre and yellow which may be arranged to resemble larger exhalent openings of compound ascidians. Yellow marks are often found near the mantle edge 
. Front edge of mantle curved into a cylindrical siphon with a cut along anterior face, so can be uncurled 
at times. Underside of mantle and upper surface of foot may be speckled with fine light grey flecks 
. No gills or tentacles on the dorsal body surface 
. Head has opaque white marks
, smooth tentacles and no snout 
. Underside of foot paler 
than dorsal body surface. Slit runs across underside of foot near front edge.
Longest dimension to about 5 mm, width to about 4 mm. Permanently enclosed in body, fragile, translucent white. Large aperture, so boat or ear shape. Spire barely perceptible, does not protrude
beyond outer lip of aperture when shell viewed in plan .
Rarely washed up intact.
Possible ambiguity over shell sizes in published accounts because of difficulty in measuring conventional height (apex to furthest point of aperture) of these fragile and unusually shaped shells, and perhaps confusion in collections of shells of L. perspicua and L.latens. Longest dimension of shell is usually half length of body.
Key identification features
If you have a record of this, or any other species of marine mollusc species, in British or Irish waters (date, place, live/dead), you are invited to inform the Marine Recorder of the Conchological Society, email firstname.lastname@example.org or submit it with image via https://www.brc.ac.uk/irecord/
- Spire barely perceptible, does not protrude beyond outer lip of aperture when shell viewed in plan .
- Opaque white marks on semi-transparent whitish head.
- Resembles a dorid sea slug [Od1] but has anterior siphon and no tentacles or gills on dorsal surface .
- Rarely, if ever, over 10mm body length or 5mm shell longest dimension.
- Body dorsum nearly smooth, with a few small tubercles .
- Profile almost flat to upturned saucer , not high dome.
- Body ground colour  can be white, light-sandy brown, or yellowish buff, but not lilac-grey.
- Body very often has fine blackish spots .
Some white animals resemble L. latens, and require examination of shell spire or head for positive identification if length of animal 10mm or less.
- NO opaque white marks on head.
- Adult body up to about 23mm, shell about 12mm longest dimension. Comparison .
- Body dorsum heavily tuberculated.
- Body profile dome to almost cone.
- Body ground colour varied, including lilac-grey.
- Short spire protrudes beyond outer lip of aperture when shell viewed in plan.
References and links
Fretter, V. and Graham, A. 1962. British prosobranch molluscs. London, Ray Society.
Graham, A. 1988. Prosobranch and pyramidellid gastropods. London.
McMillan, N.F. 1939. The British species of Lamellaria. J. Conch. Lond., 21, 170-173.
Picton, B.E. & Morrow, C.C., 2010. Encyclopedia of Marine Life of Britain and Ireland (EML) for ascidian images.