* Gymnodoris nigricolor Baba, 1960 Figure 16B

Material examined.

Two specimens 5-7 mm, SN.

Ecology.

Recorded exclusively from deeper soft sediment habitats, crawling on the substrate. Depth 19-27 m.

Distribution.

Gymnodoris nigricolor is known from the Philippines, Japan, New Caledonia, and the Solomon Islands (Gosliner et al. 2008). Here recorded as a first for Thai waters.

Remarks.

The present species closely resembles externally the description by Baba (1960) possessing a black (sometimes translucent black) dorsum and rhinophores, and a translucent foot. The gills match the description in being black, small, and club-shaped and arranged in a semi-circle. It should also be noted that the plate supplementing the original description of the species shows gills in a circular arrangement and seemingly plumose rather than reduced and club shaped. While the species is known to be parasite of gobies (Osumi and Yamasu 1994), all observations from Koh Tao were not in the vicinity of any demersal fish, including any in the family Gobiidae . Ongoing searches of gobies from both soft sediment and coral reef habitats have thus far revealed no observations of parasitic nudibranchs.