Here are a couple of pictures of comparable fossil forms:
http://www.clas.ufl.edu/users/pciesiel/gly3603c/fossils.htmlhttp://www.themissinglink.biz/images/Ebay64.jpg
The first picture shows pieces of broken mouth plates.
The second picture shows mostly pieces of stingray tail spines, but also
includes a few mouth plate segments, at top center, and the left edge center
and left edge lower.
Sorry this is not really mollusk-related, but it does address the question
that was presented.
Paul M.