Cuthona nana (Alder & Hancock, 1842)
1: translucent, white rhinophores often with opaque white pigment marks.
2: cerata more numerous than on Catriona aurantia and extend forwards of rhinophores on adults (left) but not on juveniles (right).
3: dense powdery pigment cap on cerata less extensive than on C. aurantia.
Left: Norway, June 2020. © Heine Jensen. Right: Length 6 mm. Menai Strait, Wales. March 2010.