conch ID help

[Rickyohead]

please help, I found this while snorkling in the Florida Keys. some type of conch, but I can't find good info anywhere online. it was alive, so I left it...

it was about 90% underneath the sand when I found it. it was pretty heavy; larger than my head. is this guy a rare find?!

thanks.

 

[Rickyohead]

http://www.bahamaswildlife.fsnet.co.uk/shells.htm

update:

I think it's a Emperor (Queen) Helmet