In the previous post I wrote about the 436 Donax shells I had once collected in Puerto Rico. In her comment, our regular reader Susan Hewitt asked if any of the shells had been drilled by the predatory naticid snails. As opposed to the irregular holes drilled by octopuses in the shells of their molluscan prey, the naticids (family Naticidae, moon snails) eat up their victims thru almost perfectly round holes.
A few of the Donax shells in my sample indeed have what appear to be naticid holes.
The following figure from British Prosobranch Molluscs by Fretter & Graham shows holes drilled in bivalve shells by the snails Natica (B) and Nucella (D). The former is a naticid, while the latter is in the family Muricidae.
Many more shells in the sample have chips at their edges. Here is an example.
I suspect those clams were preyed on by crabs.