>"Extreme deep-sea" mollusks have shells consisting mostly of
>protein; calcium carbonate crystals may or not be there, but I was
>surprised to poke at those brownish limpet shells only to find that
>they were sometimes very flexible. ("Extreme deep-sea" in this case
>means depths at the lower limit or well below the abyssal plains,
>i.e., below 12,000-15,000 feet. This includes the hadal fauna, or
>animals living in submarine trenches, as Fabio mentioned earlier.)

These molluscs are living below the carbonate compensation depth.

I have a specimen of Vesicomya from 8000m in the Kuril Trench. It is
shelly but has a substantial periostracum.
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
Seashell, Macintosh, VW/Toyota van nut
‚ Opinions stated are mine, not those of Otago University
"There is water at the bottom of the ocean"  - Talking Heads

----------------------------------------------------------------------
[log in to unmask] - a forum for informal discussions on molluscs
To leave this list, click on the following web link:
http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
Type your email address and name in the appropriate box and
click leave the list.
----------------------------------------------------------------------