>I've seen many shells that have been eaten by an octopus that has bored
>holes in the shells, especially Cypraea. Almost all holes in cowries are
>done by octopus. I never heard of Marginellas boring holes, thats something
>new to me.
Octopus borings are quite distinctive. Acutely colical, with
scalloped edges and often radular scrapemarks on the surrounding
shell surface; the actual perforation is very small.
>Moon snails make a concave boring. (Oyster) drills make a tubular hole.
A generalization which may not be accurate... if some muricids make
tapered holes. And any naticid boring would have to be mainly
cylindrical if it penetrated an extremely thick shell.