4, as designated by Zsilavecz, 2007, is a species of sea slug or nudibranch, a marine gastropod mollusc in the family Eubranchidae.
This is a rather small nudibranch, reaching 15 mm in total length.
It is slender and white-bodied, and it is covered with white to red yellow-tipped cerata.
The oral tentacles and rhinophores are white, smooth and short.
[1] The egg ribbon of this species is a simple upright white coil.