frame #24 Pleurobranchus sp. (don't you love nudibranchs?)

This distinct variation of the Pleurobranchus genus is not identified, though a recently published book called Nudibranchs and Sea Snails, Indo-Pacific Field Guide by Helmut Debelius has a picture of an identical nudibranch from Thailand. This book features over 1000 color plates of live shell mollusks and sea slugs, from dozens of underwater photographers - highly recommended!

Identification: unknown; therefore
Pleurobranchus sp.