>The shells in the larger rock are Turritella sp.  For some reason,
>Turritella shells are often fossilized in huge masses, and the hard
> rock containing such masses are often referred to as "turritella
> agate".

Actually, standard "Turritella agate" contains Eocene Juga spp.,
freshwater pleurocerids from the Green River Formation in Colorado and
Wyoming.  "Turritella" is a misnomer in that case.

However, the present specimens come from not far from the modern
California coast and probably represent actual turritellids.  There's a
fair amount of research that has been done on the fossils of the
general region.  The California Geological Survey website would
probably be a good source of information, or a geology department at a
nearby college.




----------------------------------------
Dr. David Campbell
425 Scientific Collections
University of Alabama, Box 870345
Tuscaloosa AL 35487
"James gave the huffle of a snail in
danger But no one heard him at all"  A.
A. Milne

----------------------------------------------------------------------
[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.
----------------------------------------------------------------------