Ident this? Pleurotus?

[Marc Palmer]

Hiya, 

Images of 3 mushrooms growing out of a maple in the UK (in a 
predominantly Yew wood)... the mushrooms amusings growing directly above 
each other in a strange step-arrangement!

Photos are at:

http://www.anyware.co.uk/marc/ident/AUT_3303.jpg 
http://www.anyware.co.uk/marc/ident/AUT_3305.jpg

One with flash, one without. I believe this to be Pleurotus dryinus / 
corticatus but there was a distinct yellowing to the undersides and stems 
which I have not seen mentioned in my books. 

The specimens were quite large - just smaller than a hand, quite spongy 
and quite pitted on top of cap from slugs etc. However they did not seem 
that old - the gills were in good condition.

Cheers