MORE DETAILED ACCOUNT AT https://flic.kr/s/aHskuaWLEz
Height (longest dimension) up to 40mm. Saucer-shape, amber-coloured. Periostracum extends into broad border beyond fragile, often fractured, calcareous layer. Aperture occupies whole of interior face.
Full-grown length about 70mm, rarely over 120mm. Oral tentacles and cephalic tentacles tubular. Two large parapodial flaps arise from mid-point of body and extend to 25% distance from posterior where they unite. Area enclosed by parapodium not close to posterior of animal. Colours and patterns vary greatly,
http://www.nudibranch.org/Scottish%20Nudibranchs/aplysia-punctata.html (J. Anderson). Mantle, enclosed by parapodial flaps, covers shell apart from large round hole; and forms erect funnel.
In shallow unpolluted water and occasionally on shores at LWS where algal food grows. Defence : colour often similar to alga it is feeding on. Can excrete milky-white acrid fluid and purple dye to screen its escape. Hermaphrodite, often several mate in a chain, http://www.nudibranch.org/Scottish%20Nudibranchs/html/aplysia-punctata-… (J.Anderson). Spawn is long tangled string .
Northern Norway to Mediterranean. Scarce or absent in Baltic and continental coast of North Sea. GBIF map http://www.gbif.org/species/5191252 . All round Britain and Ireland; except absent or scarce N.E. Irish Sea, Flamborough Head to Kent and much of east coast of Scotland. U.K. interactive map NBN https://data.nbn.org.uk/imt/?mode=SPECIES&species=NBNSYS0000173903#4-3…
The map provided here shows the distribution of the species based on Conchological Society data.