Here are a few nifty sources of info on hydrothermal vents and their fauna:

http://coa.acnatsci.org/conchnet/deepsea.html
(Very informative article by Jose Leal, with several pictures of deep
sea mollusks)

http://pw1.netcom.com/~ejpower/macab/malcabinet.htm
(Emilio Power's site, with a couple of excellent pictures of
hydrothermal vent bivalves)

http://nai.arc.nasa.gov/index.cfm?page=expedition
(This is a real-time webcast in streaming video, about hydrothermal vent
research.  I watched the first ten minutes of it, which didn't include
too much on mollusks, but there may be more info on mollusks later in
the webcast.  You need RealPlayer software to watch this.)

http://www.lgs.jussieu.fr/~intridge/fauna/ventmoll.htm
(This site used to have a complete listing of hydrothermal vent
organisms, but it doesn't seem to work now.  Unless I have it wrong?
Does anybody know?)

http://www.real.com/player/index.html?src=downloadr
(You can download RealPlayer from here if you don't have it)

Regards,
Paul M.