Aldisa zetlandica (Alder and Hancock, 1854)
A dorid nudibranch
The mantle is usually white or translucent white with white specks, but has also been recorded as greenish grey. The gills and rhinophores are also white in colour, with bushy gills which are fully retractable into a pocket. The body is elongate oval with high sides reaching 3.5 cm in length, and the back is covered with large and small conical tubercles. It has short blunt auriculate tentacles on the head. The sides of the foot are tall, and whilst the mantle is not wide it covers the head and foot. Blue or brown digestive glands may be seen through the body.