Hi Andrew,
I have not done any B&W UV photography, but I have done quite a bit of color
UV photography.  The principles should be the same, I would think.  It's
pretty easy to do, provided you have a camera that can take time exposures,
and a tripod or copy stand or some such device that will hold the camera
steady during a long exposure.  Use ordinary daylight film.  You use UV to
illuminate the specimen, however it is not reflected UV that is coming back
to the camera, or to your eye.  If it was, you wouldn't be able to see the
shell pattern, since the human eye cannot see UV rays.  Rather, what you see
is fluorescence in the visible light range, emitted by fluorescent compounds
in the shell pigments, or their remnants, in response to the UV excitation.
This can be seen by your eyes, and therefore can also be recorded on
ordinary light-sensitive film.  I haven't done much with fossils, but have
done a lot with extant species of mollusc shells.  Exposures for such
specimens range from about 30 seconds to about 3 minutes, using ASA 400
film, depending on the brightness of the fluorescent emission.  However,
some modern shells absolutely blaze with fluorescence under UV.  I suspect
that the fluorescent emission of fossils would be considerably more subtle,
in which case you would probably need even longer exposures, and also
perhaps a faster film.  I only work with longwave UV (ordinary "black
light").  No special precautions are needed with this.  Shortwave UV can
produce different fluorescent effects, but is harmful to human eyes and
skin.  If you use too weak a UV source, you will not produce the maximum
fluorescent response.  However, a fluorescent object does have a maximum
response level, and using too powerful a source just adds unwanted visible
light, without increasing fluorescent emission.  This is because a longwave
UV source emits a small percentage of visible light in the violet range,
along with the UV rays.  Longwave UV lamps can be purchased as either
fluorescent tubes or incandescent bulbs.  The bulbs are much cheaper, but in
my experience they are just about worthless for this kind of work.  They
emit far too much visible light.  The long cylindrical fluorescent tubes are
far superior.  I use two 18-inch, 15-watt tubes housed in a stainless steel
reflector, which works very well.  Good luck.
Paul Monfils