Calmella cavolini is a small aeolid (sea slug), with a maximum length of 12mm.

It has smooth elongate rhinophores, oral tentacles, and angular anterior foot corners.

Cerata, with a common stalk each, are arranged in groups.

The jaw plates are purplish red and they show through each side of the slug's head as a reddish color spot.

[1][2] Calmella cavolini is found in the Mediterranean Sea and the North Atlantic Ocean, near Europe; mainly Spain and Portugal.