Halgerda sp. from Thailand

Dear Narongpon,
In a photo it's a bit difficult to be sure, but I think this is a species of Halgerda with the gills retracted into the gill pocket, rather than a species of Reticulidia, which like all phyllidiids, would have no dorsal circlet of gills.

If it is a Halgerda I think it is an unnamed species. Not many species have been described with a white line along the mantle ridges.

Halgerda xishaensis Lin, 1975, is brown with white ridges and dark brown 'knobs' or tubercles at the junction of the ridges.

H. dalanghita has a pale whitish line edged in brownish spots, and H. albocristata has secondary white lines radiating out from the tubercles. It also has a white border with black lines at right angles to the mantle edge.

None of these species have large black or dark spots in the 'valleys' as in this animal from Surin Island. It is an interesting find Narongpon. It looks quite similar to Halgerda sp. 4. from Kerama Island, but that animal was probably a juvenile, so it hard to compare them.

Best wishes,
Bill Rudman.