These appear to fit the description of Thuridilla gracilis in Risbec (1928) and redescription in Martín-Hervás, et al (2021). In one of our darker specimens the red tip of the rhinophores was only barely visible as a reddish tint. We saw at least five of these at Mato, Ladder and Aqua Garden.
Created 14 June 2015
Updated 20 October 2021