"Probably Phyllidia carlsonhoffi, but you would need to see the bottom of the foot to be sure. Its slightly compounded larger tubercles are I think more characteristic of Phyllidia madangensis, but the small tubercles interspersed between the larger ones more match the original description of Phyllidia carlsonhoffi."
Comment from Scott Johnson
Probably Phyllidia carlsonhoffi, but you would need to see the bottom of the foot to be sure. Its slightly compounded larger tubercles are I think more characteristic of Phyllidia madangensis, but the small tubercles interspersed between the larger ones more match the original description of Phyllidia carlsonhoffi.