Any ideas about this one?

Colmani relative?

Lovely, excellent photo of a most unusual nudibranch.  I guess it may be a greedy and bloated Melibe engeli .   I will ask the nudi experts and report back.

Looks like M.engeli is a possibilitysee:

http://www.seaslugforum.net/showall/melienge

it seems quite variable.  Where was is photographed?

Romblon M. Engeli photo

The Sea Slug Forum, as Chris Ross notes, has an excellent discussion by Bill Rudman and others, of Melibe engeli and associated Melibes such as the Melibe viridis: 
http://www.seaslugforum.net/showall/melienge

and watch this one for fun:

Thanks for all the help. Found a similar photo in above article.
Smart people on Wetpixel!

As I mentioned above, I forwarded this nudibranch to Dr Terry Gosliner of the California Academy of Sciences and noted author of many books and articles on nudibranchs, who has just now replied:

"I am pretty sure this is a regenerating M. colemani where the head has been chomped by some predator. "  
 

Indeed, if one looks at the front part of this nudi with a magnifying glass, the forward cerata is not attached directly to the body but rather is floating, and there is no mouth, or head parts; they got chomped off! 
Have any of you Wetpixelers seen something like this?
What a great photo by Hulkster, with an amazing conclusion!