It's not unusual to see skulls and crossbones on graveyard headstones. The last resting place of pirates, smugglers or highwaymen you might ask. But probably not.
They are in fact Memento Mori symbols that date from around the 14th century to the Victorian age. The Latin Memento Mori roughly translates to: 'Remember that you will die'.
On some of the headstones are pictured a hourglass or egg timer. This indicates life trickling away until the ultimate journey. An hourglass on its side means the deceased was taken suddenly for whatever reason.
Apparently, some headstones depict a skull chewing on a human bone. I shall have to look for one of those!
Sadly due to age and weathering some are very feint and vague. They are fun to look for though, just watch out for the stinging nettles.
Hover over or click the image for their location.