Hi Ferran,

I´ve seen those holes from both archaeological and malacological
approaches and Paul Monfis is quite right: radula-made holes are very
easily identified from the bowl-like shape. Human-made hole are produced
by a rotating instrument of some kind, what produces a straight-walled
hole o a doble-conic when worked from both sides and concentrated in the
umbo area (which is stronger for manipulating).

In the SW Spain, Pavicardium is very commonly found in archaeological
sites too, also perforated. Regarding the engraving you mentioned, I
supposed you mean "outer part of the shell" when you say "body". If it
is so, I can tell you that the most of what I´ve seen belong to the
shell itself: the costillae are reduced and polished what give them the
appearance of engraved.

I hope this helps you.
Ana