See text Janolus is a genus of small to large sea slugs, or more accurately nudibranchs, marine gastropod mollusks, in the family Janolidae.
[2] The name Janolus is derived from the two-headed god Janus, in ancient Roman mythology.
Janolus species are found in many areas world-wide, including Europe, Australia, Japan and Africa.
This genus of nudibranch is found in shallow and subtidal waters.
When Janolus is about to be caught, it rolls into a ball, leaving its cerata exposed.