Authors: Ian Smith & Malcolm Storey. May 2012
Up to 45mm long. Smooth with no tubercles. Dark brown with green [image 8] and/or red  cast, varying with diet. Often darker when on Codium (EML) than when on other algae. Rarely pale orange . Usually speckled glistening blue or turquoise and, sometimes, green . Some have extensive white or pink marks . Two large parapodial lobes can conceal dorsum, open wide to expose it, or be held ajar . Most have a white mark on rim of each lobe . Leaf-like when upper surface of lobes bright green with dendritic  digestive gland.
Distinct groove  runs next to anterior edge of parapodial lobes and across sole, separating head from rest of body. Anterior rim thick  divided by vertical cleft into two curved halves. Large smooth enrolled rhinophores  start to grow on juveniles  when body 3mm long. No oral tentacles. Eyes clearly visible, in pale eye patches  behind rhinophores.
Sole translucent pale, tinted by viscera . Sometimes with many white or pinkish flakes  and fine brown pigment specks  . Anterior of foot swollen  but rarely extended into distinct curved propodial tentacles as drawn by Meyer & Möbius, 1865 (in Thompson, 1976). Foot expansion may give an almost pentagonal  outline to head when viewed from above. Strong transverse groove crosses sole behind head .
- Large parapodial lobes  (start to form at 3mm body length).
- Speckled with glistening blue or turquoise.
No similar British or Irish species.
Lower shore and shallow water. Reported foodplants include Codium , Cladophora , Bryopsis , Chondrus, Cytoseira, Zostera and Enteromorpha. Food preference may vary, e.g. Cladophora rupestris in Isle Of Man, but in Orkney common on Codium . Chloroplasts  are sequestered from Codium, and probably other plants, and live symbiotically in the body, presumably providing benefit for the Elysia (Taylor, 1968). Mobile parapodial lobes not used in active swimming, but may assist when drifts on currents. Large surface may assist respiration, or photosynthesis of chloroplasts. Spawn, May - October. Veliger larvae in plankton before metamorphosis.