A large, white lobed, firm slippery fungi,

A large, white lobed, firm slippery fungi,

Observation - A large, white lobed, firm slippery fungi, - UK and Ireland. Description: Unfortunately I didn't see this until it was well past its prime and starting to degrade . It was on an old cut down tree trunk, attached to the top of it by a thick stem like piece, It is not attached in any other way i.e the whole body of it is loose

Unfortunately I didn't see this until it was well past its prime and starting to degrade .
It was on an old cut down tree trunk, attached to the top of it by a thick stem like piece, It is not attached in any other way i.e the whole body of it is loose and flappy but feels firm and slightly rubbery. Pieces are about the size of my hand. the 2nd photo shows the underside which has gone black where it was lying on the wood of the trunk on top of damp leaves and moss. It has been suggested that it coud be dog=vomit Myxomycete (Fuligo septica)but looking at the 'google' pictures of this species, diverse as it is, and reading a description on
http://waynesword.palomar.edu/slime1.htm
it doesn't seem to fit. this one certainly hasn't crept anywhere!