MORE DETAILED ACCOUNT AT https://flic.kr/s/aHskD8TMGF
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Up to 40mm long, exceptionally 55mm; high dome profile. Varies white, brown, black,or yellow (P.Lightfoot) https://flic.kr/p/oJLWhQ . Pale colours may be mottled or freckled darker. Soft, tall, thin, conical tubercles on mantle give shaggy appearance, but sometimes not well developed (J.Anderson) https://flic.kr/p/Aes3Cj .
Long rhinophores often bent and tilted outwards. About 7 voluminous gills, usually with opaque white along each side of midribs forming a star.
Key identification features
2: Body soft and yielding. Usual maximum length 40mm.
3: Voluminous tripinnate gills can contract but not retract into pocket; usually, opaque white along each side of midribs forms a star when gills expanded 4Ap flic.kr/p/NKYeKt .
4: Narrow oral veil extended laterally into broad, flat oral tentacles. Anterior of veil has two protrusions centrally. 12Ap flic.kr/p/Nrc6WE
5: Upper lamellated part of large rhinophores often bent backwards 7Ap flic.kr/p/NQxst9 .
On mid- and lower-shore and sublittorally to about 170m. Adults occur in all months; commonest in spring when spawning at maximum. Spawn an undulating ribbon attached in a spiral of few turns.