Old Tailrace - artefacts 2

Various creatures small and large, probably relating to different periods. The most curious seems to be oyster shells, simply because there is no obvious reason for them to be here. One idea is that oysters were thought to be part of the staple diet of monks who may have been local. Records exist stating that the monks of St Radigunds Abbey owned a 13th Century watermill somewhere in "crabble". Could it have been here?